ozone: Dispatch GPU process IPCs to IO thread directly from GpuPlatformSupportHost

ozone: Dispatch GPU process IPCs to IO thread directly from GpuPlatformSupportHost

This takes an (IO thread) TaskRunner & callback pair instead of an
IPC::Sender when we establish the GPU channel, so that we'll be able to
send messages to the GPU process from browser threads without passing
through the UI thread.

This is preparatory work to allow us to bypass the browser UI thread for
cursor updates on freon builds. It doesn't change the code to send
messages from other threads yet.

BUG=446184
TEST=Boot link_freon to login screen

Committed: https://crrev.com/d128d1293da9bf11aefcb335b4e94bdc9f85374d
Cr-Commit-Position: refs/heads/master@{#310917}

[spang, 2015-01-09 20:58:42]

spang@chromium.org changed reviewers:
+ alexst@chromium.org, piman@chromium.org

[alexst (slow to review), 2015-01-09 21:53:08]

lgtm

https://codereview.chromium.org/821133006/diff/1/ui/ozone/public/ui_thread_gp...
File ui/ozone/public/ui_thread_gpu.cc (right):

https://codereview.chromium.org/821133006/diff/1/ui/ozone/public/ui_thread_gp...
ui/ozone/public/ui_thread_gpu.cc:70: ->OnChannelEstablished(kGpuProcessHostId,
task_runner_, sender);
You call them send_runner and send_callback in other parts of the code, maybe
keep those names here for consistency.

[piman, 2015-01-09 23:32:19]

lgtm

[spang, 2015-01-10 00:04:30]

The CQ bit was checked by spang@chromium.org

[commit-bot: I haz the power, 2015-01-10 00:05:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/821133006/1

[commit-bot: I haz the power, 2015-01-10 00:35:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-01-10 00:36:24]

Patchset 1 (id:??) landed as
https://crrev.com/d128d1293da9bf11aefcb335b4e94bdc9f85374d
Cr-Commit-Position: refs/heads/master@{#310917}