[Merge M50] Ensure that native WindowAndroid outlives native AwContents.

[Merge M50] Ensure that native WindowAndroid outlives native AwContents.

ContentViewCore holds a window pointer that is used during
destruction of native AwContents to remove observers. However the
current CleanupReference based finalization scheme does not enforce
an ordering on the destruction of native WindowAndroid and AwContents
instances. Satisfaction of the constraint that AwContents is destroyed
before WindowAndroid is therefore dependent on the CleanupReference
implementation, and possibly the implementation of the JVM as well.

Making the AwContents DestroyRunnable strongly reference the
associated WindowAndroidWrapper enforces the correct ordering.

BUG=595336
Review URL: https://codereview.chromium.org/1809643002

Cr-Commit-Position: refs/heads/master@{#381675}
(cherry picked from commit 81a813fcee09c1ed0f299aba3b589e3705238875)

BUG=599216
Committed: https://chromium.googlesource.com/chromium/src/+/beebc994b0b69df0b32921601ff32506f2664254

[boliu, 2016-03-30 21:50:20]

Description was changed from

==========
[Merge M50] Ensure that native WindowAndroid outlives native AwContents.

ContentViewCore holds a window pointer that is used during
destruction of native AwContents to remove observers. However the
current CleanupReference based finalization scheme does not enforce
an ordering on the destruction of native WindowAndroid and AwContents
instances. Satisfaction of the constraint that AwContents is destroyed
before WindowAndroid is therefore dependent on the CleanupReference
implementation, and possibly the implementation of the JVM as well.

Making the AwContents DestroyRunnable strongly reference the
associated WindowAndroidWrapper enforces the correct ordering.

BUG=595336

Review URL: https://codereview.chromium.org/1809643002

Cr-Commit-Position: refs/heads/master@{#381675}
(cherry picked from commit 81a813fcee09c1ed0f299aba3b589e3705238875)

BUG=599216
==========

to

==========
[Merge M50] Ensure that native WindowAndroid outlives native AwContents.

ContentViewCore holds a window pointer that is used during
destruction of native AwContents to remove observers. However the
current CleanupReference based finalization scheme does not enforce
an ordering on the destruction of native WindowAndroid and AwContents
instances. Satisfaction of the constraint that AwContents is destroyed
before WindowAndroid is therefore dependent on the CleanupReference
implementation, and possibly the implementation of the JVM as well.

Making the AwContents DestroyRunnable strongly reference the
associated WindowAndroidWrapper enforces the correct ordering.

BUG=595336

Review URL: https://codereview.chromium.org/1809643002

Cr-Commit-Position: refs/heads/master@{#381675}
(cherry picked from commit 81a813fcee09c1ed0f299aba3b589e3705238875)

BUG=599216

Committed:
https://chromium.googlesource.com/chromium/src/+/beebc994b0b69df0b32921601ff3...
==========

[boliu, 2016-03-30 21:50:22]

Committed patchset #1 (id:1) manually as
beebc994b0b69df0b32921601ff32506f2664254.