cc: Implement overdraw feedback debugging feature.

components/display_compositor/buffer_queue.cc

Index: components/display_compositor/buffer_queue.cc
diff --git a/components/display_compositor/buffer_queue.cc b/components/display_compositor/buffer_queue.cc
index a827812a7796c5a4ee545b129d7d68b9e694cd84..afb40e1a4912accfc68929b8d7b72d70e7ac8cb8 100644
--- a/components/display_compositor/buffer_queue.cc
+++ b/components/display_compositor/buffer_queue.cc
@@ -60,6 +60,10 @@ void BufferQueue::BindFramebuffer() {
   if (current_surface_) {
     gl_->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                               texture_target_, current_surface_->texture, 0);
+    if (current_surface_->stencil) {
+      gl_->FramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT,
+                                   GL_RENDERBUFFER, current_surface_->stencil);
+    }
   }
 }
 
@@ -115,8 +119,10 @@ void BufferQueue::SwapBuffers(const gfx::Rect& damage) {
 
 void BufferQueue::Reshape(const gfx::Size& size,
                           float scale_factor,
-                          const gfx::ColorSpace& color_space) {
-  if (size == size_ && color_space == color_space_)
+                          const gfx::ColorSpace& color_space,
+                          bool use_stencil) {
+  if (size == size_ && color_space == color_space_ &&
+      use_stencil == use_stencil_)
     return;
 #if !defined(OS_MACOSX)
   // TODO(ccameron): This assert is being hit on Mac try jobs. Determine if that
@@ -126,11 +132,13 @@ void BufferQueue::Reshape(const gfx::Size& size,
 #endif
   size_ = size;
   color_space_ = color_space;
+  use_stencil_ = use_stencil;
 
-  // TODO: add stencil buffer when needed.
   gl_->BindFramebuffer(GL_FRAMEBUFFER, fbo_);
   gl_->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                             texture_target_, 0, 0);
+  gl_->FramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT,
+                               GL_RENDERBUFFER, 0);
 
   FreeAllSurfaces();
 }
@@ -200,6 +208,8 @@ void BufferQueue::FreeSurfaceResources(AllocatedSurface* surface) {
   gl_->ReleaseTexImage2DCHROMIUM(texture_target_, surface->image);
   gl_->DeleteTextures(1, &surface->texture);
   gl_->DestroyImageCHROMIUM(surface->image);
+  if (surface->stencil)
+    gl_->DeleteRenderbuffers(1, &surface->stencil);
   surface->buffer.reset();
   allocated_count_--;
 }
@@ -215,6 +225,15 @@ std::unique_ptr<BufferQueue::AllocatedSurface> BufferQueue::GetNextSurface() {
   GLuint texture;
   gl_->GenTextures(1, &texture);
 
+  GLuint stencil = 0;
+  if (use_stencil_) {
+    gl_->GenRenderbuffers(1, &stencil);
+    gl_->BindRenderbuffer(GL_RENDERBUFFER, stencil);
+    gl_->RenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, size_.width(),
+                             size_.height());
+    gl_->BindRenderbuffer(GL_RENDERBUFFER, 0);
+  }
+
   // We don't want to allow anything more than triple buffering.
   DCHECK_LT(allocated_count_, 4U);
   std::unique_ptr<gfx::GpuMemoryBuffer> buffer(
@@ -240,7 +259,7 @@ std::unique_ptr<BufferQueue::AllocatedSurface> BufferQueue::GetNextSurface() {
   gl_->BindTexture(texture_target_, texture);
   gl_->BindTexImage2DCHROMIUM(texture_target_, id);
   return base::MakeUnique<AllocatedSurface>(this, std::move(buffer), texture,
-                                            id, gfx::Rect(size_));
+                                            id, stencil, gfx::Rect(size_));
 }
 
 BufferQueue::AllocatedSurface::AllocatedSurface(
@@ -248,11 +267,13 @@ BufferQueue::AllocatedSurface::AllocatedSurface(
     std::unique_ptr<gfx::GpuMemoryBuffer> buffer,
     uint32_t texture,
     uint32_t image,
+    uint32_t stencil,
     const gfx::Rect& rect)
     : buffer_queue(buffer_queue),
       buffer(buffer.release()),
       texture(texture),
       image(image),
+      stencil(stencil),
       damage(rect) {}
 
 BufferQueue::AllocatedSurface::~AllocatedSurface() {