GitLab

Modify content SynchronousCompositor related classes to
support for content embedder to use delegated rendering. The
embedder is responsible for creating the parent compositor.
Essentially need to pass CompositorFrame and
CompositorFrameAck between embedder and
SynchronousCompositor. Also need to expose the share context
so embedder can correctly initialize a context for parent
compositor.

In android_webview implemented parent compositor for
delegated rendering while keeping the current direct
renderer working, controlled by a command line switch.

BrowserViewRenderer deals exclusively with
SynchronousCompositor (the child). And HardwareRenderer
deals exclusively with the parent compositor. The two share
data through lock protected SharedRendererState. And all are
coordinated by native AwContents.

Direct rendering path is kept alive in
HardwareRendererLegacy and code guarded by
switches::UbercompEnabled. Direct rendering path remains the
default.

BUG=344087

Review URL: https://codereview.chromium.org/287993004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272668 0039d316-1c4b-4281-b951-d872f2087c98