Tiling priorities in Android Webview.

android_webview/browser/hardware_renderer.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/hardware_renderer.h"
 
 #include "android_webview/browser/aw_gl_surface.h"
 #include "android_webview/browser/deferred_gpu_command_service.h"
 #include "android_webview/browser/parent_output_surface.h"
 #include "android_webview/browser/shared_renderer_state.h"
@@ skipping 189 matching lines @@
   delegated_layer_->SetTransform(transform);
 
   gl_surface_->SetBackingFrameBufferObject(framebuffer_binding_ext);
   {
     base::AutoReset<bool> frame_resetter(&viewport_clip_valid_for_dcheck_,
                                          true);
     layer_tree_host_->SetNeedsRedrawRect(clip_);
     layer_tree_host_->Composite(gfx::FrameTime::Now());
   }
   gl_surface_->ResetBackingFrameBufferObject();
+
+  // Need to post the new transform matrix back to child compositor
+  // because there is no onDraw during a Render Thread animation, and child
+  // compositor might not have the tiles rasterized as the animation goes on.
+  ParentCompositorDrawConstraints draw_constraints(
+      draw_info->is_layer, transform, gfx::Rect(viewport_));
+  if (!draw_constraints_.equals(draw_constraints)) {

[boliu, 2014/07/29 19:02:41]

Remember we are not looking for "equals" exactly. We don't care about the
surface size if we are not in a layer.

Let's move this block near the beginning of the method, let's say right after
checking context changed.

[hush (inactive), 2014/07/29 21:14:21]

Yeah.

Why do we want to move this to the beginning of the function? Just to reduce a
little bit of latency when you post it to UI?
Also for the record, this portion of the code will be in "DrawGL" after I rebase
past kModeSync CL: https://codereview.chromium.org/414163002/
On 2014/07/29 19:02:41, boliu wrote:

+    draw_constraints_ = draw_constraints;
+    shared_renderer_state_->PostExternalDrawConstraintsToChildCompositor(
+        draw_constraints);
+  }
 }
 
 scoped_ptr<cc::OutputSurface> HardwareRenderer::CreateOutputSurface(
     bool fallback) {
   // Android webview does not support losing output surface.
   DCHECK(!fallback);
   scoped_refptr<cc::ContextProvider> context_provider =
       CreateContext(gl_surface_,
                     DeferredGpuCommandService::GetInstance(),
                     shared_renderer_state_->GetSharedContext());
   scoped_ptr<ParentOutputSurface> output_surface_holder(
       new ParentOutputSurface(context_provider));
   output_surface_ = output_surface_holder.get();
   return output_surface_holder.PassAs<cc::OutputSurface>();
 }
 
 void HardwareRenderer::UnusedResourcesAreAvailable() {
   cc::ReturnedResourceArray returned_resources;
   resource_collection_->TakeUnusedResourcesForChildCompositor(
       &returned_resources);
   shared_renderer_state_->InsertReturnedResources(returned_resources);
 }
 
 }  // namespace android_webview