Rename BeginFrame to BeginMainFrame and BeginImplFrame in cc::SchedulerStateMachine.

First patch in a series to rename BeginFrame. This patch focuses on
cc::SchedulerStateMachine.

In the scheduler, the term 'BeginFrame' is used for both the main thread and the
impl thread. This can cause confusion if it's not obvious which one is being
refered to. To clarify this, we rename BeginFrame to BeginMainFrame and
BeginImplFrame, respectively.

BUG=261765

Review URL: https://codereview.chromium.org/26969004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229599 0039d316-1c4b-4281-b951-d872f2087c98
Remove message loop parameter from RenderThreadImpl::GetGpuFactories()

RenderThreadImpl::GetGpuFactories() makes the assumption that all the
GpuVideoAcceleratorFactories retrieved from it can use the same 3D context.
This is only true if all the factories use the same message loop for the
3D context.  Ensure this by unconditionally using
RenderThreadImpl::GetMediaThreadMessageLoopProxy() for that message loop.

This change should be a functional no-op according to the current
architecture.

BUG=306333
TEST=local build, run on CrOS snow, build on desktop Linux

Review URL: https://codereview.chromium.org/27019011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229600 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229599
SVN changes up to revision 229600
Call NaClProcessHost::EarlyStartup on the IO thread rather than the UI thread.

BUG=292679

Review URL: https://codereview.chromium.org/27048005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229601 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229601