Implement chrome.screenlockPrivate.showMessage API function.

BUG=320156
TEST=manual

Review URL: https://codereview.chromium.org/102793002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238778 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238778
Introduce gpu::Capabilities

gpu::Capabilities is a subset of FeatureInfo that is exposed
to the command buffer client.

It is populated in GlES2Implementation::Initialize,
piggy-backing on the synchronous init ipc.

Make ContextProviderInProcess use gpu::Capabilities as well
instead of hardcoding them.

Merged GpuControl::SupportsGpuMemoryBuffer into capabilities.

BUG=285390

Review URL: https://codereview.chromium.org/73263003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238779 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238779