Fix blank video in Android WebView

Fix blank video in Android WebView

This bug is introduced in r324679. When Initialize/ReleaseHardware was
removed, the call to the factory the kept a count on the number of
compositors with hardware acceleration was dropped. This means the
factory refuses to create a context for video.

Add those callbacks, and emulate the original call by checking if the
memory policy is zero.

Committed: https://crrev.com/5ddc6ffcc0bda6d9a25613fb96adee249de135e7
Cr-Commit-Position: refs/heads/master@{#325345}

[boliu, 2015-04-15 22:57:21]

boliu@chromium.org changed reviewers:
+ hush@chromium.org

[boliu, 2015-04-15 22:57:21]

ptal

[sgurun-gerrit only, 2015-04-15 23:21:39]

sgurun@chromium.org changed reviewers:
+ sgurun@chromium.org

[sgurun-gerrit only, 2015-04-15 23:21:40]

lgtm

[boliu, 2015-04-15 23:22:26]

The CQ bit was checked by boliu@chromium.org

[commit-bot: I haz the power, 2015-04-15 23:23:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1073893004/1

[commit-bot: I haz the power, 2015-04-15 23:41:15]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-15 23:42:10]

Patchset 1 (id:??) landed as
https://crrev.com/5ddc6ffcc0bda6d9a25613fb96adee249de135e7
Cr-Commit-Position: refs/heads/master@{#325345}