Revert 186627

Revert 186627

Speculative revert. The tree went red at the time this change was checked in, and multiple GpuFeatureTests started failing consistently.

Example failure: http://test-results.appspot.com/dashboards/flakiness_dashboard.html#group=@DEPS - chromium.org&testType=browser_tests&tests=GpuFeatureTest.WebGLAllowed
If you look at the first Win Aura Tests (2) fail, you get the following blamelist range: 186630 to 186619.

> Use gpu::Mailbox in IPCs instead of std::string
> 
> gpu::Mailbox is safer since the size is checked in the deserializer. It's also
> overall less code.
> 
> BUG=None
> 
> 
> Review URL: https://chromiumcodereview.appspot.com/12440005

TBR=piman@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=186758

[miu, 2013-03-07 19:32:33]

Committed patchset #1 manually as r186758.