Revert of Remove compositor-only entry points from WebGraphicsContext3D (https://codereview.chromium.org/134743002/)

Reason for revert:
../../content/browser/renderer_host/compositor_impl_android.cc: In member function 'virtual blink::WebGLId content::CompositorImpl::GenerateTexture(gfx::JavaBitmap&)':
../../content/browser/renderer_host/compositor_impl_android.cc:306:12: error: 'class blink::WebGraphicsContext3D' has no member named 'shallowFlushCHROMIUM'

Original issue's description:
> Remove compositor-only entry points from WebGraphicsContext3D
> 
> This removes entry points from blink::WebGraphicsContext3D that were only
> being used by the compositor.  This interface should have the entry points
> needed by WebGL only.
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=165249

TBR=kbr@chromium.org
NOTREECHECKS=true
NOTRY=true

Review URL: https://codereview.chromium.org/140883006

git-svn-id: svn://svn.chromium.org/blink/trunk@165251 bbb929c8-8fbe-4397-9dbb-9b2b20218538