Set an initial background for RenderFrameHosts during commit.

Set an initial background for RenderFrameHosts during commit.

This was originally implemented in https://codereview.chromium.org/2466413009,
but was broken by https://codereview.chromium.org/2496233003. Now re-adding
with more explicit code, plus a unittest.

BUG=470669
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2733093002
Cr-Commit-Position: refs/heads/master@{#455612}
(cherry picked from commit 5f3c1abd7dc2df3024315ec66eb46e89a5e146c8)

Review-Url: https://codereview.chromium.org/2738983004 .
Cr-Commit-Position: refs/branch-heads/3029@{#95}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/68d43f9c021c6259b25a0594d7a0d1a1505ee0dc

[chrishtr, 2017-03-09 22:45:34]

Description was changed from

==========
Set an initial background for RenderFrameHosts during commit.

This was originally implemented in https://codereview.chromium.org/2466413009,
but was broken by https://codereview.chromium.org/2496233003. Now re-adding
with more explicit code, plus a unittest.

BUG=470669
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2733093002
Cr-Commit-Position: refs/heads/master@{#455612}
(cherry picked from commit 5f3c1abd7dc2df3024315ec66eb46e89a5e146c8)
==========

to

==========
Set an initial background for RenderFrameHosts during commit.

This was originally implemented in https://codereview.chromium.org/2466413009,
but was broken by https://codereview.chromium.org/2496233003. Now re-adding
with more explicit code, plus a unittest.

BUG=470669
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2733093002
Cr-Commit-Position: refs/heads/master@{#455612}
(cherry picked from commit 5f3c1abd7dc2df3024315ec66eb46e89a5e146c8)

Review-Url: https://codereview.chromium.org/2738983004 .
Cr-Commit-Position: refs/branch-heads/3029@{#95}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/68d43f9c021c6259b25a0594d7a0...
==========

[chrishtr, 2017-03-09 22:45:35]

Committed patchset #1 (id:1) manually as
68d43f9c021c6259b25a0594d7a0d1a1505ee0dc.