[Android WebView] Implement Ubercomp for Render Thread support

android_webview/browser/parent_output_surface.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "android_webview/browser/parent_output_surface.h"
+
+#include "cc/output/output_surface_client.h"
+#include "gpu/command_buffer/client/gles2_interface.h"
+
+namespace android_webview {
+
+ParentOutputSurface::ParentOutputSurface(
+    scoped_refptr<cc::ContextProvider> context_provider)
+    : cc::OutputSurface(context_provider) {
+  capabilities_.draw_and_swap_full_viewport_every_frame = true;
+}
+
+ParentOutputSurface::~ParentOutputSurface() {
+}
+
+void ParentOutputSurface::SwapBuffers(cc::CompositorFrame* frame) {
+  context_provider_->ContextGL()->ShallowFlushCHROMIUM();
+  client_->DidSwapBuffers();
+}
+
+void ParentOutputSurface::SetDrawConstraints(const gfx::Size& surface_size,
+                                             const gfx::Rect& clip) {
+  DCHECK(client_);
+  surface_size_ = surface_size;
+  SetNeedsRedrawRect(gfx::Rect(surface_size));

[danakj, 2014/05/21 15:45:39]

Do you need this given the caps flag to draw the full frame always?

[boliu, 2014/05/21 15:54:16]

Yes this is still needed. draw_and_swap_full_viewport_every_frame was one the
settings added just for webview, but *after* webview already had
SetNeedsRedrawRect before each draw. So instead of changing cc internally, we
just added some DCHECKs that there's always damage from the OutputSurface:

https://code.google.com/p/chromium/codesearch#chromium/src/cc/trees/layer_tre...
https://code.google.com/p/chromium/codesearch#chromium/src/cc/trees/layer_tre...

I guess it's a bit counter-intuitive, but I think it does makes sense for cc to
assume OutputSurface behaves a certain way, since this is an OutputSurface
capability after all.

+  gfx::Transform identity;
+  gfx::Rect empty;
+  SetExternalDrawConstraints(identity, empty, clip, true);
+}
+
+}  // namespace android_webview