dont mutate from frame to frame

We'll need to make this fancier as the compositor gets smarter.

Instead of squashing the layers down into a single SkPicture, we now pass the
tree to the GPU thread, which draws everything separately.

Previously we were using the cull rect of the SkPicture to size the GPU buffer,
but Skia is too smart and shrinkwraps the cull rect, which meant we weren't
sizing the GPU buffer to the right size.

Fixes #814

Previously there was a race condition when updating the size of the GLSurface.
Now we explicitly update the size of the surface to match what we expect.

Fixes #610

We used to do this in the SkPicture, but it's simpler to do it in the
rasterizer now that we're using multiple SkPictures in Dart.

Now that we can use WTF everywhere, we don't need to use skia::RefPtr.

@abarth

R=ianh@google.com

Review URL: https://codereview.chromium.org/1235813005 .

When navigating from one app to another, we create a new Android window and
destroy the old one. Previously, when we destroyed the old window after
creating the new window, we would destroy the Ganesh context after making the
GL context for the new window current, causing us to corrupt the GL state in
the new window. After this CL, we call MakeCurrent before destroying the Ganesh
context so that it interacts with the proper GL context.

R=jackson@google.com

Review URL: https://codereview.chromium.org/1214263002.

BUG=
R=iansf@google.com

Review URL: https://codereview.chromium.org/1183213007.

Update the native_viewport interface to allow specification of the surface configuration, currently only needed for and used by EGL on Android.

This also fixes an issue where eglChooseConfig was
only being called in InitializeOneOff, which is
only called once per process.  This CL makes
choosing the config happen once per GLSurface
instead, which will ultimately permit apps to
create multiple native_viewports with different
surface configurations on the same display.  The
eglDisplay object is still a global, though.

R=abarth@chromium.org, viettrungluu@chromium.org, jamesr@chromium.org

Review URL: https://codereview.chromium.org/1168993002.

These will help us better understand what's happening.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/1027913002

Sometimes we try to draw a 0x0 picture. We shouldn't bother trying to turn a
0x0 picture into actual pixels.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/984153004

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

This CL plumbs resize notifications from SkyView to Engine. I've taken the
opportunity to reorganize how notifications generated by SkyView are plumbed to
the GPU and UI threads. This approach should reduce the amount of plumbing
needed for new notifications.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/880443003

This CL adds support to SkyShell for drawing with Ganesh. Currently, we don't
actually create any SkPictures to draw, but that will come in a later CL.

R=eseidel@chromium.org

Review URL: https://codereview.chromium.org/891143002