Fix white flash on certain Chromecast screen transitions.

Fix white flash on certain Chromecast screen transitions.

Reboot and brain freeze screens can lead be followed by seeing the
browser compositor's background colour, which defaults to white.

BUG=internal b/19379351

Committed: https://crrev.com/431bafe9608acb5afb6e53ab97963b62d3e4ec48
Cr-Commit-Position: refs/heads/master@{#317705}

[halliwell, 2015-02-23 23:38:54]

halliwell@chromium.org changed reviewers:
+ lcwu@chromium.org

[gunsch, 2015-02-23 23:39:57]

On 2015/02/23 23:38:59, halliwell wrote:

lgtm, but

is there a bug you can point this at? "BUG=internal b/XXXXXX" is an acceptable
pattern

[lcwu1, 2015-02-23 23:45:28]

lgtm

[halliwell, 2015-02-23 23:46:15]

The CQ bit was checked by halliwell@chromium.org

[halliwell, 2015-02-23 23:46:15]

The patchset sent to the CQ was uploaded after l-g-t-m from gunsch@chromium.org
Link to the patchset: https://codereview.chromium.org/950123002/#ps20001 (title:
"Add bug link.")

[commit-bot: I haz the power, 2015-02-23 23:52:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/950123002/20001

[commit-bot: I haz the power, 2015-02-24 01:01:56]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-24 01:03:01]

Patchset 2 (id:??) landed as
https://crrev.com/431bafe9608acb5afb6e53ab97963b62d3e4ec48
Cr-Commit-Position: refs/heads/master@{#317705}