The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ff2b583208f110e3217e5879a6681b3e1875f7bb

commit ff2b583208f110e3217e5879a6681b3e1875f7bb
Author: carlosk <carlosk@chromium.org>
Date: Fri Oct 28 02:08:44 2016

Offline Page Cache: do not save a snapshot of a page loaded from a snapshot.

Offline Page Cache was saving snapshots of pages being loaded from
previously saved snapshots, which is unnecessary. This change fixes that
by only enabling the saving if the loaded page is not an "offline" page
itself.

BUG= 660106 

Review-Url: https://codereview.chromium.org/2448143005
Cr-Commit-Position: refs/heads/master@{#428239}

[modify] https://crrev.com/ff2b583208f110e3217e5879a6681b3e1875f7bb/chrome/browser/android/offline_pages/recent_tab_helper.cc

I'd like to merge commit ff2b583208f110e3217e5879a6681b3e1875f7bb into M55.

Your change meets the bar and is auto-approved for M55 (branch: 2883)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/55afac3f35ed774b0a1cd79985f495e158fc2da3

commit 55afac3f35ed774b0a1cd79985f495e158fc2da3
Author: Carlos Knippschild <carlosk@chromium.org>
Date: Fri Oct 28 22:38:48 2016

Offline Page Cache: do not save a snapshot of a page loaded from a snapshot.

Offline Page Cache was saving snapshots of pages being loaded from
previously saved snapshots, which is unnecessary. This change fixes that
by only enabling the saving if the loaded page is not an "offline" page
itself.

BUG= 660106 

Review-Url: https://codereview.chromium.org/2448143005
Cr-Commit-Position: refs/heads/master@{#428239}
(cherry picked from commit ff2b583208f110e3217e5879a6681b3e1875f7bb)

Review URL: https://codereview.chromium.org/2462713003 .

Cr-Commit-Position: refs/branch-heads/2883@{#368}
Cr-Branched-From: 614d31daee2f61b0180df403a8ad43f20b9f6dd7-refs/heads/master@{#423768}

[modify] https://crrev.com/55afac3f35ed774b0a1cd79985f495e158fc2da3/chrome/browser/android/offline_pages/recent_tab_helper.cc

Reopening this because I realized we should also have test coverage for this error. If that was the case this error would not have re-appeared in the first place.

Fixit update: great for fixit. Now that we have an instrumentation test for RecentTabHelper [1] simulating this situation will be much easier (versus with the unit test).

[1] https://cs.chromium.org/chromium/src/chrome/android/javatests/src/org/chromium/chrome/browser/offlinepages/RecentTabsTest.java

Lowering priority as the remaining work is a good to have but not a need.

Created Issue 786481 to track the need of a regression test. Closing this one.