cc: Without valid frame, delegated renderer layer is not drawable

cc/delegated_renderer_layer_impl.cc

 // Copyright 2012 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 "cc/delegated_renderer_layer_impl.h"
 
 #include "cc/append_quads_data.h"
 #include "cc/delegated_frame_data.h"
 #include "cc/layer_tree_impl.h"
 #include "cc/math_util.h"
@@ skipping 28 matching lines @@
 void DelegatedRendererLayerImpl::SetFrameData(
     scoped_ptr<DelegatedFrameData> frame_data,
     gfx::RectF damage_in_frame) {
   CreateChildIdIfNeeded();
   DCHECK(child_id_);
 
   // Display size is already set so we can compute what the damage rect
   // will be in layer space.
   RenderPass* new_root_pass = frame_data->render_pass_list.empty() ?
                               NULL : frame_data->render_pass_list.back();
-  bool new_frame_is_empty = !new_root_pass;
 
-  RenderPass* old_root_pass = render_passes_in_draw_order_.empty() ?
-                              NULL : render_passes_in_draw_order_.back();
-  bool old_frame_is_empty = !old_root_pass;
-
-  gfx::RectF damage_in_layer;
-  if (new_frame_is_empty) {
-    if (!old_frame_is_empty)
-      damage_in_layer = gfx::Rect(bounds());
-  } else {
+  if (new_root_pass) {

[piman, 2013/02/27 21:04:35]

pushing even slightly further, you can save an if by testing
!frame_data->render_pass_list.empty() here and only fetching
frame_data->render_pass_list.back() inside the if.

[danakj, 2013/02/27 21:05:27]

True! Let's see how the remap CL looks, I can do that there.

[danakj, 2013/02/27 21:40:45]

Oh right, this is waiting on CQ from another CL anyways. Done!

     DCHECK(!new_root_pass->output_rect.IsEmpty());
-    damage_in_layer = MathUtil::mapClippedRect(
+    gfx::RectF damage_in_layer = MathUtil::mapClippedRect(
         DelegatedFrameToLayerSpaceTransform(new_root_pass->output_rect.size()),
         damage_in_frame);
+    setUpdateRect(gfx::UnionRects(updateRect(), damage_in_layer));
   }
-  setUpdateRect(gfx::UnionRects(updateRect(), damage_in_layer));
 
   // TODO(danakj): Convert the resource ids the render passes and return data
   // for a frame ack.
   SetRenderPasses(frame_data->render_pass_list);
 }
 
 void DelegatedRendererLayerImpl::SetDisplaySize(gfx::Size size) {
   if (display_size_ == size)
     return;
   display_size_ = size;
@@ skipping 211 matching lines @@
 void DelegatedRendererLayerImpl::ClearChildId() {
   if (!child_id_)
     return;
 
   ResourceProvider* resource_provider = layerTreeImpl()->resource_provider();
   resource_provider->destroyChild(child_id_);
   child_id_ = 0;
 }
 
 }  // namespace cc