@abarth

Now we actually use the vsync signal to trigger work. Previously, we'd hit the
pipeline depth limit too early and fall back to swap buffers-triggered
rendering.

Also, rename Vsync to VSync on recommendation from jamesr.

Instead of using back pressure from swap buffers to drive the engine, this
patch using the vsync signal from the Android framework. We still respect
back pressure from swap buffers if we get too far ahead.

Previously, there was a race condition whereby we could end up with three
requests in the pipeline. Now we update the number of outstanding requests
synchronously, which avoids the race.

This DCHECK is triggering due to my recent change. Remove it while I debug.

Previously, we weren't overlapping any work between the UI and the GPU threads
because each waited for the other to finish. After this patch, we now have a
pipeline depth of 2, which means we can be working on two frames at once, one
for each thread.  In the future, we should dynamically adjust the pipeline
depth.

This listens to both surface destruction as well as activity
pause/unpause.

R=abarth@chromium.org, abarth@google.com

Review URL: https://codereview.chromium.org/1230073002 .

This CL adds trace events:

1) Between requesting a frame and begin frame.
2) In the DartLoader see network latency.
3) While executing |main| and |_init|.

TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1025073003

However WebView::close() no longer crashes.  close() is never called
in MojoShell since mojo can't shutdown yet.

I tried closing the existing WebView and replacing it
but somehow that caused it to only draw red.  After a while
of looking at this with abarth we decided to just load into
the same WebView for now.

Eventually we should do something smarter where we start the
provisional load and only replace the webview once the new one is
ready, but that's a later CL.

R=abarth@chromium.org
BUG=

Review URL: https://codereview.chromium.org/952273003

This CL contains enough plumbing for Sky to render content to the screen using
Ganesh in SkyShell. We're still missing the ability to load data off the
network.

R=eseidel@chromium.org, ojan@chromium.org

Review URL: https://codereview.chromium.org/936883002