The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/2abcf0413069159c73bceba72f0b6f124021bca5

commit 2abcf0413069159c73bceba72f0b6f124021bca5
Author: petewil <petewil@chromium.org>
Date: Mon Apr 10 21:45:00 2017

Get signals working in the EXTRA_DATA section of MHTML

The intent of this change is to add some signal data to the bottom of
a MHTML file when generating an offline file if the new OfflinePagesLoadSignalCollecting flag is set.  The signal data
will be analyzed to find a better time to take snapshots, and will eventually be used to decide at runtime when to take snapshots.  Design docs here:
https://docs.google.com/document/d/1AcoZOIb81V68_KDSOCatFSYYMLOTSYj6resg-VAxLgo

BUG= 706628 

Review-Url: https://codereview.chromium.org/2683493002
Cr-Commit-Position: refs/heads/master@{#463407}

[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/about_flags.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/android/offline_pages/prerendering_loader.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/android/offline_pages/prerendering_loader.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/android/offline_pages/prerendering_offliner.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/android/offline_pages/prerendering_offliner.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/android/offline_pages/prerendering_offliner_unittest.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/flag_descriptions.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/chrome/browser/flag_descriptions.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/components/offline_pages/core/offline_page_feature.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/components/offline_pages/core/offline_page_feature.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/components/offline_pages/core/offline_page_model_impl_unittest.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/browser/BUILD.gn
[add] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/browser/download/mhtml_extra_parts_impl.cc
[add] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/browser/download/mhtml_extra_parts_impl.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/browser/download/mhtml_generation_browsertest.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/browser/download/mhtml_generation_manager.cc
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/public/browser/BUILD.gn
[add] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/content/public/browser/mhtml_extra_parts.h
[modify] https://crrev.com/2abcf0413069159c73bceba72f0b6f124021bca5/tools/metrics/histograms/histograms.xml

Additional work is required:
Add a way to send extra headers as headers instead of in the body.
Make the extra data JSON.
Add loading signal data to the BackgroundLoaderOfflienr

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/73cbc9649a4cda766fbedb4e27d38872f87f5018

commit 73cbc9649a4cda766fbedb4e27d38872f87f5018
Author: petewil <petewil@chromium.org>
Date: Tue Apr 18 20:50:58 2017

Write loading signal extra data in JSON

Our first attempt wrote siganls in plain text strings.  We think
they will be easier to handle and more extensible if we use JSON
instead.

BUG= 706628 

Review-Url: https://codereview.chromium.org/2821133003
Cr-Commit-Position: refs/heads/master@{#465359}

[modify] https://crrev.com/73cbc9649a4cda766fbedb4e27d38872f87f5018/chrome/browser/android/offline_pages/prerendering_loader.cc
[modify] https://crrev.com/73cbc9649a4cda766fbedb4e27d38872f87f5018/chrome/browser/android/offline_pages/prerendering_loader.h
[modify] https://crrev.com/73cbc9649a4cda766fbedb4e27d38872f87f5018/chrome/browser/android/offline_pages/prerendering_offliner.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/39358c18ce1cc85f8d11144800c88c4146cc6b14

commit 39358c18ce1cc85f8d11144800c88c4146cc6b14
Author: petewil <petewil@chromium.org>
Date: Wed Apr 19 17:21:40 2017

Add extra headers argument so we don't pass headers in the body.

In the first implementation, we passed extra headers inside the body, a CR comment identified that it would be better to pass them separately, this change separates them out into a different input parameter.

BUG= 706628 

Review-Url: https://codereview.chromium.org/2827503002
Cr-Commit-Position: refs/heads/master@{#465650}

[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/chrome/browser/android/offline_pages/prerendering_offliner.cc
[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/content/browser/download/mhtml_extra_parts_impl.cc
[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/content/browser/download/mhtml_extra_parts_impl.h
[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/content/browser/download/mhtml_generation_browsertest.cc
[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/content/browser/download/mhtml_generation_manager.cc
[modify] https://crrev.com/39358c18ce1cc85f8d11144800c88c4146cc6b14/content/public/browser/mhtml_extra_parts.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b00919686f1472b84a9f928aa22af4d47b0ffd5a

commit b00919686f1472b84a9f928aa22af4d47b0ffd5a
Author: petewil <petewil@chromium.org>
Date: Thu Apr 20 17:46:35 2017

Collect loading signal data from the background loader offliner

We currently collect loading signal from the prerendering offliner, but
not the background loader offliner.  This adds collection from the
background loader offliner too.  The signals will be sent as JSON.

BUG= 706628 

Review-Url: https://codereview.chromium.org/2819393002
Cr-Commit-Position: refs/heads/master@{#466056}

[modify] https://crrev.com/b00919686f1472b84a9f928aa22af4d47b0ffd5a/chrome/browser/android/offline_pages/background_loader_offliner.cc
[modify] https://crrev.com/b00919686f1472b84a9f928aa22af4d47b0ffd5a/chrome/browser/android/offline_pages/background_loader_offliner.h
[modify] https://crrev.com/b00919686f1472b84a9f928aa22af4d47b0ffd5a/chrome/browser/android/offline_pages/background_loader_offliner_unittest.cc