cc: Implement overdraw feedback debugging feature.

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 2af2c3091e04adaea2d2c0b298383a841be91659..993ef4483144cf69d1744b1b8639d6433c30cfbc 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -6,6 +6,7 @@
 #define CC_OUTPUT_GL_RENDERER_H_
 
 #include <deque>
+#include <set>
 #include <vector>
 
 #include "base/cancelable_callback.h"
@@ -270,6 +271,14 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
   void ScheduleRenderPassDrawQuad(const CALayerOverlay* ca_layer_overlay,
                                   DrawingFrame* external_frame);
 
+  // Setup/flush all pending overdraw feedback to frambuffer.
+  void SetupOverdrawFeedback();
+  void FlushOverdrawFeedback(const DrawingFrame* frame,
+                             const gfx::Rect& output_rect);
+  // Process overdraw feedback from query.
+  void OverdrawFeedback(unsigned query, int category, base::Closure barrier);
+  void UpdateOverdrawCounter() const;
+
   using OverlayResourceLock =
       std::unique_ptr<ResourceProvider::ScopedReadLockGL>;
   using OverlayResourceLockList = std::vector<OverlayResourceLock>;
@@ -543,6 +552,13 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
 
   BoundGeometry bound_geometry_;
   ColorLUTCache color_lut_cache_;
+
+  std::set<int> current_overdraw_;

[Daniele Castagna, 2017/01/09 18:53:06]

Why don't you just use std::bitset here?

[Daniele Castagna, 2017/01/09 18:53:06]

Why don't you just use std::bitset here?

[reveman, 2017/01/10 23:52:01]

That requires knowing the number of overdraw categories here at compile time
(ie. std::bitset<num_categories>) or use a magic value here. I prefer to keep
that as simple as a size of an array in the .cc file.

[reveman, 2017/01/11 03:22:02]

Fyi, follow up patch that uses SAMPLES_PASSED_ARB for more accurate trace events
will also require this to become a map instead of a set.

+  unsigned offscreen_stencil_renderbuffer_id_ = 0;
+  gfx::Size offscreen_stencil_renderbuffer_size_;
+  struct PendingOverdrawQuery;
+  std::deque<std::unique_ptr<PendingOverdrawQuery>> pending_overdraw_queries_;
+
   DISALLOW_COPY_AND_ASSIGN(GLRenderer);
 };