[Offline pages] Stop observing web contents and reset to null after use. Only create a new web cont…

[Offline pages] Stop observing web contents and reset to null after use. Only create a new web contents when we need it. (M59 merge)

Before this change, we will create a new webcontents in preparation for a request that might not come in for hours or days. During the waiting period, a number of things can happen which may result in things related to the webcontents to become stale and therefore crash when we actually do use it. One hypothesis is that a render process host might be created without any render processes attached to it, causing the host to be removed under certain memory pressures or when certain clean-up processes are triggered.

For better memory and freshness, we should probably only create a web contents when we actually need it anyway, and clean up everything after we use it.

BUG=714272, 709443
Review-Url: https://codereview.chromium.org/2866643005
Cr-Original-Commit-Position: refs/heads/master@{#469906}
Review-Url: https://codereview.chromium.org/2873393004 .
Cr-Commit-Position: refs/branch-heads/3071@{#521}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/339b80c4f9ff8e29b73b0842570be8b852f2340f

[carlosk, 2017-05-11 22:44:56]

Description was changed from

==========
[Offline pages] Stop observing web contents and reset to null after use. Only
create a new web contents when we need it. (M59 merge)

Before this change, we will create a new webcontents in preparation for a
request that might not come in for hours or days. During the waiting period, a
number of things can happen which may result in things related to the
webcontents to become stale and therefore crash when we actually do use it. One
hypothesis is that a render process host might be created without any render
processes attached to it, causing the host to be removed under certain memory
pressures or when certain clean-up processes are triggered.

For better memory and freshness, we should probably only create a web contents
when we actually need it anyway, and clean up everything after we use it.

BUG=714272,709443

Review-Url: https://codereview.chromium.org/2866643005
Cr-Commit-Position: refs/heads/master@{#469906}
(cherry picked from commit e427c75396a3388f0b64915128a371bb1c5793f0)
==========

to

==========
[Offline pages] Stop observing web contents and reset to null after use. Only
create a new web contents when we need it. (M59 merge)

Before this change, we will create a new webcontents in preparation for a
request that might not come in for hours or days. During the waiting period, a
number of things can happen which may result in things related to the
webcontents to become stale and therefore crash when we actually do use it. One
hypothesis is that a render process host might be created without any render
processes attached to it, causing the host to be removed under certain memory
pressures or when certain clean-up processes are triggered.

For better memory and freshness, we should probably only create a web contents
when we actually need it anyway, and clean up everything after we use it.

BUG=714272,709443

Review-Url: https://codereview.chromium.org/2866643005
Cr-Original-Commit-Position: refs/heads/master@{#469906}
Review-Url: https://codereview.chromium.org/2873393004 .
Cr-Commit-Position: refs/branch-heads/3071@{#521}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/339b80c4f9ff8e29b73b0842570b...
==========

[carlosk, 2017-05-11 22:44:57]

Committed patchset #1 (id:1) manually as
339b80c4f9ff8e29b73b0842570be8b852f2340f.