The migration code is being added here: https://codereview.chromium.org/2862353003/diff/1/android_webview/java/src/org/chromium/android_webview/AwBrowserProcess.java

"No patch exists with that ID" :), what's the reason for the migration logic?

Ah ok, it's I see the CL now 

Updated link: https://codereview.chromium.org/2862353003/diff/60001/android_webview/java/src/org/chromium/android_webview/AwBrowserProcess.java

(Sorry, I messed up some git commands, so ended up deleting the original patch set.)

The NextAction date has arrived: 2017-06-05

We decided in the code review that it might be better to wait a few milestones prior to fully removing these old code paths, as some users might skip a version or two when upgrading Chrome.  I'll also be traveling a bunch during the summer, so pushing this out 'til August.

The NextAction date has arrived: 2017-08-15

What was the case in which this could fail? (or where we might drop some files)

We could drop files if users have some pending crash reports, and never ran a version of Chrome that contained the migration logic.  However, at this point it's probably the case that any pending crash reports from such old versions are not too interesting to us, especially for users who aren't stuck on those old versions.

https://chromium-review.googlesource.com/c/616253

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/788cbde709274b58a80d246d8274e5b4fd5a11ff

commit 788cbde709274b58a80d246d8274e5b4fd5a11ff
Author: Ilya Sherman <isherman@chromium.org>
Date: Mon Aug 21 20:22:55 2017

[Cleanup] Remove some temporary filename migration logic.

R=gsennton@chromium.org

Bug:  719120 
Change-Id: Ia79a95b278d1f1af6ba8c00a522d39a94f32b03f
Reviewed-on: https://chromium-review.googlesource.com/616253
Reviewed-by: Gustav Sennton <gsennton@chromium.org>
Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Reviewed-by: Maria Khomenko <mariakhomenko@chromium.org>
Commit-Queue: Ilya Sherman <isherman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#496044}
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/android_webview/java/src/org/chromium/android_webview/crash/AwMinidumpUploaderDelegate.java
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/chrome/android/java/src/org/chromium/chrome/browser/crash/ChromeMinidumpUploaderDelegate.java
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/components/minidump_uploader/android/java/src/org/chromium/components/minidump_uploader/CrashFileManager.java
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/components/minidump_uploader/android/java/src/org/chromium/components/minidump_uploader/MinidumpUploaderDelegate.java
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/components/minidump_uploader/android/java/src/org/chromium/components/minidump_uploader/MinidumpUploaderImpl.java
[modify] https://crrev.com/788cbde709274b58a80d246d8274e5b4fd5a11ff/components/minidump_uploader/android/javatests/src/org/chromium/components/minidump_uploader/TestMinidumpUploaderDelegate.java