Thanks for writing up the document! The plan looks great to me :)

One question is: What do you mean by "disabling" some dump provider (for performance and/or memory reasons)? Does it mean that no number will be reported by the dump provider? Or the dump provider only reports representative numbers without scanning its heap?

If we worry about performance and/or memory impacts, in v0 we can just start with reporting representative numbers from each dump provider (e.g., effective_size etc). The numbers will be helpful to understand overview of real-world memory usages. If we find any problem there, we can manually open the URL and collect more detailed results (e.g., object types). If the performance and memory look good, in v1 we can expand tracing data for the background mode.

My point is just that we can start with clearly non-controversial parts, and then iterate :) What do you think?

Yes that is the plan. We have the dump providers provide a light dump of just totals.
Disabling a dump provider is to not dump anything. This is because the light dump itself is very heavy. The version 1 is the plan to try and aggregate them and add just a total.
Yes, I agree with going with the non-controversial parts in V0. I have put controversial providers as "disabled" for V1.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/13ebc734eab7950938afbfac677080604d972d91

commit 13ebc734eab7950938afbfac677080604d972d91
Author: ssid <ssid@chromium.org>
Date: Tue May 31 21:01:04 2016

[tracing] Introduce BACKGROUND mode in MemoryInfra

This CL makes following changes:
1. Adds a BACKGROUND mode in the dump triggers in trace config.
1. Periodic dumps can be disabled on passing 0 as interval.
2. On BACKGROUND mode only whitelisted dump providers are invoked.
3. Clean up periodic dump timer set up.
4. MemoryDumpSessionState is initialized with config in the renderer
   also.

BUG= 613198 

Review-Url: https://codereview.chromium.org/1995573003
Cr-Commit-Position: refs/heads/master@{#396927}

[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/memory_dump_manager.cc
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/memory_dump_manager.h
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/memory_dump_manager_unittest.cc
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/memory_dump_request_args.cc
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/memory_dump_request_args.h
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/trace_config_memory_test_util.h
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/base/trace_event/trace_config_unittest.cc
[modify] https://crrev.com/13ebc734eab7950938afbfac677080604d972d91/components/tracing/child_trace_message_filter_browsertest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3011f204cda084e39ce76d93b62d885b57c8a2bf

commit 3011f204cda084e39ce76d93b62d885b57c8a2bf
Author: ssid <ssid@chromium.org>
Date: Wed Jun 01 20:24:26 2016

[tracing] Fix V8 and PartitionAlloc dump provider for background mode

For background mode, just dump same details as light mode.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2013643005
Cr-Commit-Position: refs/heads/master@{#397228}

[modify] https://crrev.com/3011f204cda084e39ce76d93b62d885b57c8a2bf/gin/v8_isolate_memory_dump_provider.cc
[modify] https://crrev.com/3011f204cda084e39ce76d93b62d885b57c8a2bf/third_party/WebKit/Source/platform/PartitionAllocMemoryDumpProvider.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/83ec5cba3d1f054875044a674c34aec22c2033c3

commit 83ec5cba3d1f054875044a674c34aec22c2033c3
Author: ssid <ssid@chromium.org>
Date: Fri Jun 03 00:14:37 2016

[tracing] Support background mode in skia memory dump provider

Background mode requires quick dump and just the totals, to be
able to collect traces in the background for all users.
Skia dump provider adds just the cache sizes in background mode.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2015763003
Cr-Commit-Position: refs/heads/master@{#397552}

[modify] https://crrev.com/83ec5cba3d1f054875044a674c34aec22c2033c3/skia/ext/skia_memory_dump_provider.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cc85367ae9abe6221f7a5427689095157295a720

commit cc85367ae9abe6221f7a5427689095157295a720
Author: ssid <ssid@chromium.org>
Date: Fri Jun 03 05:12:11 2016

[tracing] Only add totals from discardable memory in background mode

For background tracing mode only totals can be added to the trace to
keep traces light. So only add total numbers from discardable memory
dump provider.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2012763004
Cr-Commit-Position: refs/heads/master@{#397639}

[modify] https://crrev.com/cc85367ae9abe6221f7a5427689095157295a720/content/child/child_discardable_shared_memory_manager.cc
[modify] https://crrev.com/cc85367ae9abe6221f7a5427689095157295a720/content/common/host_discardable_shared_memory_manager.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8ed45166343233d13a8f3517a0b8b33d9907248f

commit 8ed45166343233d13a8f3517a0b8b33d9907248f
Author: ssid <ssid@chromium.org>
Date: Sat Jun 04 08:13:26 2016

Set up background memory light tracing field trials

This CL introduces a BENCHMARK_MEMORY_LIGHT mode for background field
trials to enable memory-infra category in BACKGROUND mode. The
background tracing controller disables the periodic memory dumps and
takes a single memory snapshot when a light preset is passed.
Since the BACKGROUND mode in memory-infra is restricted only to
whitelisted dump providers (currently empty), this tracing mode causes
very low overhead (currently none) on the user experience.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2034553002
Cr-Commit-Position: refs/heads/master@{#397910}

[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/base/trace_event/trace_config.cc
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/base/trace_event/trace_config.h
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/content/browser/tracing/background_tracing_config_impl.cc
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/content/browser/tracing/background_tracing_config_impl.h
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/content/browser/tracing/background_tracing_config_unittest.cc
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/content/browser/tracing/background_tracing_manager_impl.cc
[modify] https://crrev.com/8ed45166343233d13a8f3517a0b8b33d9907248f/content/browser/tracing/background_tracing_manager_impl.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/448e5edbdae14ce8b983726b9d89d248f3d52d23

commit 448e5edbdae14ce8b983726b9d89d248f3d52d23
Author: ssid <ssid@chromium.org>
Date: Sat Jun 04 12:40:51 2016

[tracing] Sanitize process memory dump names for background mode

For background mode:
1. ProcessMemoryDump knows the level of detail.
2. It checks for dump name to be present in whitelist. If not then
   returns a dummy mad. The strings are stripped of numbers (ids) and
   checked against a whitelist of dump names.
3. Disable creating new dumps just to mark suballocations.
4. Disable creation of global allocator dumps.
5. Disable string attributes in allocator dumps.
Also creates a new whitelist file to handle whitelisting logic.

BUG= 613198 
TBR=shess@chromium.org, jochen@chromium.org

Review-Url: https://codereview.chromium.org/2006943003
Cr-Commit-Position: refs/heads/master@{#397918}

[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/BUILD.gn
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/java_heap_dump_provider_android_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_allocator_dump.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_allocator_dump_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_dump_manager.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_dump_manager.h
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_dump_manager_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_dump_provider.h
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_dump_request_args.h
[add] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_infra_background_whitelist.cc
[add] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/memory_infra_background_whitelist.h
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/process_memory_dump.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/process_memory_dump.h
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/process_memory_dump_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/trace_event.gypi
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/base/trace_event/winheap_dump_provider_win_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/components/tracing/common/graphics_memory_dump_provider_android_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/components/tracing/common/process_metrics_memory_dump_provider_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/content/common/discardable_shared_memory_heap_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/gin/v8_isolate_memory_dump_provider_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/skia/ext/skia_memory_dump_provider_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/sql/connection_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/sql/sql_memory_dump_provider_unittest.cc
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/third_party/WebKit/Source/platform/heap/BlinkGCMemoryDumpProvider.cpp
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/third_party/WebKit/Source/platform/heap/BlinkGCMemoryDumpProviderTest.cpp
[modify] https://crrev.com/448e5edbdae14ce8b983726b9d89d248f3d52d23/third_party/WebKit/Source/platform/web_process_memory_dump.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/496beec77470f6b9d9c40051ab71318b3dd227ea

commit 496beec77470f6b9d9c40051ab71318b3dd227ea
Author: ssid <ssid@chromium.org>
Date: Tue Jun 07 02:44:08 2016

[tracing] Fix light dump of partition alloc dump provider

Partition Alloc dump provider dumps bucket stats for the case of
DirectMap objects even for ligth dumps. This CL fixes this issue.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2045643002
Cr-Commit-Position: refs/heads/master@{#398206}

[modify] https://crrev.com/496beec77470f6b9d9c40051ab71318b3dd227ea/third_party/WebKit/Source/wtf/allocator/PartitionAlloc.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/659a76cbecfd264aa1c04c113e5d0a03b88038fc

commit 659a76cbecfd264aa1c04c113e5d0a03b88038fc
Author: ssid <ssid@chromium.org>
Date: Wed Jun 08 07:19:15 2016

[tracing] Support background mode in dom storage memory dumps

Provide just total numbers for background mode dumps in dom storage.
The storage could be using memory for commit batches along with the
storage maps. So, add the size to tracing.

BUG= 613198 ,  605785 
TBR=michaeln

Review-Url: https://codereview.chromium.org/1950893003
Cr-Commit-Position: refs/heads/master@{#398499}

[modify] https://crrev.com/659a76cbecfd264aa1c04c113e5d0a03b88038fc/content/browser/dom_storage/dom_storage_area.cc
[modify] https://crrev.com/659a76cbecfd264aa1c04c113e5d0a03b88038fc/content/browser/dom_storage/dom_storage_context_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/4205d7b56a9ea78e8fc1c229963019edfe02910f

commit 4205d7b56a9ea78e8fc1c229963019edfe02910f
Author: ssid <ssid@chromium.org>
Date: Wed Jun 15 20:36:03 2016

[tracing] Replace %p with %PRIXPTR in the memory dump names

The tracing dump names for memory-infra were inconsistent across
platforms since %p prints 0x on posix and prints the number without
markers in Windows. To make the names consistent, %p is replaced with
PRIXPTR with a standard marker "0x".

BUG= 613198 
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel
TBR=jochen@chromium.org, skyostil@chromium.org

Review-Url: https://codereview.chromium.org/2067543003
Cr-Commit-Position: refs/heads/master@{#400004}

[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/cc/tiles/gpu_image_decode_controller.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/cc/tiles/software_image_decode_controller.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/content/browser/dom_storage/dom_storage_area.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/content/browser/dom_storage/dom_storage_context_impl.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/content/browser/dom_storage/session_storage_database.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/content/browser/indexed_db/leveldb/leveldb_database.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/extensions/browser/value_store/leveldb_value_store.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/gin/v8_isolate_memory_dump_provider.cc
[modify] https://crrev.com/4205d7b56a9ea78e8fc1c229963019edfe02910f/sql/connection_memory_dump_provider.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3f4573d82141b7e36438f84ab12fcf9a20725e1e

commit 3f4573d82141b7e36438f84ab12fcf9a20725e1e
Author: ssid <ssid@chromium.org>
Date: Thu Jun 16 01:00:49 2016

[tracing] Set whitelist values for dump provider supporting background mode

Adds list of strings to whitelist.
Modifies stripping logic to make the whitelist readable.
The whitelisted dump providers support background mode efficiently.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2012883003
Cr-Commit-Position: refs/heads/master@{#400064}

[modify] https://crrev.com/3f4573d82141b7e36438f84ab12fcf9a20725e1e/base/trace_event/memory_infra_background_whitelist.cc
[modify] https://crrev.com/3f4573d82141b7e36438f84ab12fcf9a20725e1e/base/trace_event/process_memory_dump_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c442e187b9c818fe715817b332bbb1f3aaa38301

commit c442e187b9c818fe715817b332bbb1f3aaa38301
Author: ssid <ssid@chromium.org>
Date: Fri Jun 17 02:57:42 2016

[tracing] Add browser test for background memory tracing

This CL adds a browser test for background mode memory tracing.
To start tracing in background mode, trace config string must be passed
with background mode trigger. So, this CL edits the tracing test to
support trace config strings.

This CL also removes the single process test for tracing since single
process mode is not supported well.

Discardable dump provider creates dumps with same name from browser and
renderer and this is not allowed in single process mode. So, child ids
are added to the dumps.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2047533002
Cr-Commit-Position: refs/heads/master@{#400333}

[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/base/trace_event/memory_dump_manager_unittest.cc
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/base/trace_event/trace_config_memory_test_util.h
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/base/trace_event/trace_config_unittest.cc
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/chrome/test/base/tracing.cc
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/chrome/test/base/tracing.h
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/chrome/test/base/tracing_browsertest.cc
[modify] https://crrev.com/c442e187b9c818fe715817b332bbb1f3aaa38301/content/child/child_discardable_shared_memory_manager.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7d2fd66cc632f2fcf5fb821936cdac319f7f8233

commit 7d2fd66cc632f2fcf5fb821936cdac319f7f8233
Author: ssid <ssid@chromium.org>
Date: Thu Jun 23 18:13:51 2016

Move memory-infra check from background tracing and whitelist memory dump args

BUG= 613198 

Review-Url: https://codereview.chromium.org/2092463002
Cr-Commit-Position: refs/heads/master@{#401652}

[modify] https://crrev.com/7d2fd66cc632f2fcf5fb821936cdac319f7f8233/base/trace_event/memory_dump_manager.cc
[modify] https://crrev.com/7d2fd66cc632f2fcf5fb821936cdac319f7f8233/chrome/common/trace_event_args_whitelist.cc
[modify] https://crrev.com/7d2fd66cc632f2fcf5fb821936cdac319f7f8233/content/browser/tracing/background_tracing_manager_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22

commit a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22
Author: dgozman <dgozman@chromium.org>
Date: Thu Jun 23 21:28:16 2016

Revert of Move memory-infra check from background tracing and whitelist memory dump args (patchset #1 id:20001 of https://codereview.chromium.org/2092463002/ )

Reason for revert:
Speculative revert. Looks like this could have broken mac and linux sizes: https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/21314

Original issue's description:
> Move memory-infra check from background tracing and whitelist memory dump args
>
> BUG= 613198 
>
> Committed: https://crrev.com/7d2fd66cc632f2fcf5fb821936cdac319f7f8233
> Cr-Commit-Position: refs/heads/master@{#401652}

TBR=primiano@chromium.org,oysteine@chromium.org,ssid@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG= 613198 

Review-Url: https://codereview.chromium.org/2095593003
Cr-Commit-Position: refs/heads/master@{#401725}

[modify] https://crrev.com/a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22/base/trace_event/memory_dump_manager.cc
[modify] https://crrev.com/a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22/chrome/common/trace_event_args_whitelist.cc
[modify] https://crrev.com/a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22/content/browser/tracing/background_tracing_manager_impl.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/111f2d475c3e7a0bf621439bc48f7aac22acb16a

commit 111f2d475c3e7a0bf621439bc48f7aac22acb16a
Author: ssid <ssid@chromium.org>
Date: Fri Jun 24 02:12:53 2016

Reland of Move memory-infra check from background tracing and whitelist memory dump args (patchset #1 id:1 of https://codereview.chromium.org/2095593003/ )

Reason for reland:
Changing the category to use const char* string "memory-infra" instead of the static member kTraceCategory, to avoid static initialization.

Original issue's description:
> Revert of Move memory-infra check from background tracing and whitelist memory dump args (patchset #1 id:20001 of https://codereview.chromium.org/2092463002/ )
>
> Reason for revert:
> Speculative revert. Looks like this could have broken mac and linux sizes: https://build.chromium.org/p/chromium/builders/Linux%20x64/builds/21314
>
> Original issue's description:
> > Move memory-infra check from background tracing and whitelist memory dump args
> >
> > BUG= 613198 
> >
> > Committed: https://crrev.com/7d2fd66cc632f2fcf5fb821936cdac319f7f8233
> > Cr-Commit-Position: refs/heads/master@{#401652}
>
> TBR=primiano@chromium.org,oysteine@chromium.org,ssid@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG= 613198 
>
> Committed: https://crrev.com/a8b0d1386ef9ae3f3f45316c0e5bd4d39a8e5a22
> Cr-Commit-Position: refs/heads/master@{#401725}

TBR=primiano@chromium.org,oysteine@chromium.org,dgozman@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
BUG= 613198 

Review-Url: https://codereview.chromium.org/2090953004
Cr-Commit-Position: refs/heads/master@{#401790}

[modify] https://crrev.com/111f2d475c3e7a0bf621439bc48f7aac22acb16a/base/trace_event/memory_dump_manager.cc
[modify] https://crrev.com/111f2d475c3e7a0bf621439bc48f7aac22acb16a/chrome/common/trace_event_args_whitelist.cc
[modify] https://crrev.com/111f2d475c3e7a0bf621439bc48f7aac22acb16a/content/browser/tracing/background_tracing_manager_impl.cc

Background tracing is enabled :)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/61d80b31a3f83987b8a7eab9f812fbb56f330658

commit 61d80b31a3f83987b8a7eab9f812fbb56f330658
Author: ssid <ssid@chromium.org>
Date: Fri Jul 29 21:29:51 2016

Background Tracing: Remove safety check for crash exit on Android

On Android the exit status is always marked as EXIT_CRASHED. So, the
background traces are never uploaded. Since the check is useful only for
preemptive mode, this CL removes this check for REACTIVE triggers on
Android and adds extra check for preemptive trigger in that place.

BUG= 613198 

Review-Url: https://codereview.chromium.org/2192093002
Cr-Commit-Position: refs/heads/master@{#408771}

[modify] https://crrev.com/61d80b31a3f83987b8a7eab9f812fbb56f330658/chrome/browser/tracing/chrome_tracing_delegate.cc

 Issue 556977  has been merged into this issue.