Make Editor::revealSelectionAfterEditingOperation check document availability

Make Editor::revealSelectionAfterEditingOperation check document availability

The above mentioned function is called to reveal selection after a user
initiated editing operation. However, it shouldn't proceed if the operation
destroys the frame, which is ensured by this patch.

BUG=685347
TEST=LayoutTests/editing/inserting/insert_linebreak_remove_frame.html

Review-Url: https://codereview.chromium.org/2653063004
Cr-Commit-Position: refs/heads/master@{#446275}
(cherry picked from commit 4b7ec96e0cdf6ef721b15a31ea88d4c868f38929)

Review-Url: https://codereview.chromium.org/2666513002 .
Cr-Commit-Position: refs/branch-heads/2987@{#165}
Cr-Branched-From: ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed: https://chromium.googlesource.com/chromium/src/+/5b0c94296eb74cc8109e0aecf4342deba60dae19

[Xiaocheng, 2017-01-30 06:15:58]

Description was changed from

==========
Make Editor::revealSelectionAfterEditingOperation check document availability

The above mentioned function is called to reveal selection after a user
initiated editing operation. However, it shouldn't proceed if the operation
destroys the frame, which is ensured by this patch.

BUG=685347
TEST=LayoutTests/editing/inserting/insert_linebreak_remove_frame.html

Review-Url: https://codereview.chromium.org/2653063004
Cr-Commit-Position: refs/heads/master@{#446275}
(cherry picked from commit 4b7ec96e0cdf6ef721b15a31ea88d4c868f38929)
==========

to

==========
Make Editor::revealSelectionAfterEditingOperation check document availability

The above mentioned function is called to reveal selection after a user
initiated editing operation. However, it shouldn't proceed if the operation
destroys the frame, which is ensured by this patch.

BUG=685347
TEST=LayoutTests/editing/inserting/insert_linebreak_remove_frame.html

Review-Url: https://codereview.chromium.org/2653063004
Cr-Commit-Position: refs/heads/master@{#446275}
(cherry picked from commit 4b7ec96e0cdf6ef721b15a31ea88d4c868f38929)

Review-Url: https://codereview.chromium.org/2666513002 .
Cr-Commit-Position: refs/branch-heads/2987@{#165}
Cr-Branched-From:
ad51088c0e8776e8dcd963dbe752c4035ba6dab6-refs/heads/master@{#444943}
Committed:
https://chromium.googlesource.com/chromium/src/+/5b0c94296eb74cc8109e0aecf434...
==========

[Xiaocheng, 2017-01-30 06:16:01]

Committed patchset #1 (id:1) manually as
5b0c94296eb74cc8109e0aecf4342deba60dae19.