android webview: allow cc to fail hardware draw

content/renderer/android/synchronous_compositor_output_surface.cc

Index: content/renderer/android/synchronous_compositor_output_surface.cc
diff --git a/content/renderer/android/synchronous_compositor_output_surface.cc b/content/renderer/android/synchronous_compositor_output_surface.cc
index 39dea1b080e33180bfcf8c393b575f806492dd42..ac50424cf606333b4ccc8bbabc032bb423b7873e 100644
--- a/content/renderer/android/synchronous_compositor_output_surface.cc
+++ b/content/renderer/android/synchronous_compositor_output_surface.cc
@@ -76,7 +76,6 @@ SynchronousCompositorOutputSurface::SynchronousCompositorOutputSurface(
       frame_swap_message_queue_(frame_swap_message_queue) {
   thread_checker_.DetachFromThread();
   DCHECK(registry_);
-  capabilities_.draw_and_swap_full_viewport_every_frame = true;
   capabilities_.adjust_deadline_for_parent = false;
   capabilities_.delegated_rendering = true;
   capabilities_.max_frames_pending = 1;
@@ -195,7 +194,9 @@ void SynchronousCompositorOutputSurface::InvokeComposite(
   SetExternalDrawConstraints(adjusted_transform, viewport, clip,
                              viewport_rect_for_tile_priority,
                              transform_for_tile_priority, !hardware_draw);
-  SetNeedsRedrawRect(gfx::Rect(viewport.size()));
+  if (!hardware_draw) {
+    SetNeedsRedrawRect(gfx::Rect(viewport.size()));

[brianderson, 2015/10/22 20:53:35]

Does this also need to be called for the first hardware draw after a software
draw? Or alternatively accumulate the damage rects of all previous software
draws and union that with the damage for the first hardware draw?

[boliu, 2015/10/22 20:57:53]

Good question. I think the answer is yes.

This is proably better: move all this damage logic into LTHI::OnDraw as well.
Then for software, save the damage at the beginning, damage viewport, draw, and
restore the old damage. That would be the "right" behavior I think?

[boliu, 2015/10/22 21:50:08]

Keeping it at the end of InvokeComposite here for now.

+  }
 
   client_->OnDraw();