cc: Implement overdraw feedback debugging feature.

cc/output/direct_renderer.cc

Index: cc/output/direct_renderer.cc
diff --git a/cc/output/direct_renderer.cc b/cc/output/direct_renderer.cc
index d0798231bcb21092967c4ca6161b0881e6b54360..8f0e1df7b1c0762b4645d44981dc21de84d779c8 100644
--- a/cc/output/direct_renderer.cc
+++ b/cc/output/direct_renderer.cc
@@ -87,6 +87,11 @@ void DirectRenderer::Initialize() {
       context_provider->ContextCapabilities().commit_overlay_planes)
     allow_empty_swap_ = true;
 
+  overdraw_feedback_ = settings_->overdraw_feedback &&
+                       output_surface_->capabilities().supports_stencil;
+  LOG_IF(WARNING, overdraw_feedback_ != settings_->overdraw_feedback)
+      << "Overdraw feedback enabled without output surface stencil support.";
+
   initialized_ = true;
 }
 
@@ -238,6 +243,7 @@ void DirectRenderer::DrawFrame(RenderPassList* render_passes_in_draw_order,
   // can leave the window at the wrong size if we never draw and the proper
   // viewport size is never set.
   bool frame_has_alpha = frame.root_render_pass->has_transparent_background;
+  bool use_stencil = overdraw_feedback_;
   if (device_viewport_size != reshape_surface_size_ ||
       device_scale_factor != reshape_device_scale_factor_ ||
       device_color_space != reshape_device_color_space_ ||
@@ -246,9 +252,9 @@ void DirectRenderer::DrawFrame(RenderPassList* render_passes_in_draw_order,
     reshape_device_scale_factor_ = device_scale_factor;
     reshape_device_color_space_ = device_color_space;
     reshape_has_alpha_ = frame.root_render_pass->has_transparent_background;
-    output_surface_->Reshape(reshape_surface_size_,
-                             reshape_device_scale_factor_,
-                             reshape_device_color_space_, reshape_has_alpha_);
+    output_surface_->Reshape(
+        reshape_surface_size_, reshape_device_scale_factor_,
+        reshape_device_color_space_, reshape_has_alpha_, use_stencil);
   }
 
   BeginDrawingFrame(&frame);