Add logic to GLRenderer to support RenderPassDrawQuad copying.

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 30c227367f04c417ca458243429848b411ac9214..51b4c907c33a752bc94c6124e390ab0f0ec68b90 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -35,6 +35,7 @@ namespace cc {
 class GLRendererShaderTest;
 class OutputSurface;
 class PictureDrawQuad;
+class ResourcePool;
 class ScopedResource;
 class StreamVideoDrawQuad;
 class TextureDrawQuad;
@@ -263,6 +264,16 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
   void ScheduleCALayers(DrawingFrame* frame);
   void ScheduleOverlays(DrawingFrame* frame);
 
+  // Indicates that an overlay resource with the given |texture| id is no longer
+  // in use.
+  void OverlayResourceNoLongerInUse(GLuint texture);
+
+  // Copies the contents of the render pass to an overlay resource, returned in
+  // |resource_id|. The resource is allocated from |overlay_resource_pool_|, and
+  // stays allocated until OverlayResourceNoLongerInUse() is called.
+  void CopyRenderPassToOverlayResource(const RenderPassId& render_pass_id,
+                                       ResourceId* resource_id);
+
   using OverlayResourceLock =
       std::unique_ptr<ResourceProvider::ScopedReadLockGL>;
   using OverlayResourceLockList = std::vector<OverlayResourceLock>;
@@ -521,6 +532,10 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
   bool use_blend_equation_advanced_;
   bool use_blend_equation_advanced_coherent_;
 
+  // Some overlays require that content is copied from a render pass into an
+  // overlay resource. This means the GLRenderer needs its own ResourcePool.
+  std::unique_ptr<ResourcePool> overlay_resource_pool_;

[ccameron, 2016/07/20 22:13:53]

I'd add a
  std::map<ResourceId, Resource*> overlay_pool_resources_in_use_
and then ... (cut to gl_render.cc)

+
   BoundGeometry bound_geometry_;
   DISALLOW_COPY_AND_ASSIGN(GLRenderer);
 };