cc: Don't draw and swap if the frame will not change.

cc/trees/layer_tree_host_unittest_delegated.cc

 // Copyright 2013 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/trees/layer_tree_host.h"
 
 #include "cc/layers/delegated_renderer_layer.h"
 #include "cc/layers/delegated_renderer_layer_impl.h"
 #include "cc/output/delegated_frame_data.h"
 #include "cc/quads/shared_quad_state.h"
@@ skipping 231 matching lines @@
   }
 
   virtual bool PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
                                      LayerTreeHostImpl::FrameData* frame,
                                      bool result) OVERRIDE {
     EXPECT_TRUE(result);
 
     if (!first_draw_for_source_frame_)
       return result;
 
-    gfx::RectF damage_rect = frame->render_passes.back()->damage_rect;
+    gfx::RectF damage_rect;
+    if (!frame->has_no_damage) {
+      damage_rect = frame->render_passes.back()->damage_rect;
+    } else {
+      // If there is no damage, then we have no render passes to send.
+      EXPECT_TRUE(frame->render_passes.empty());
+    }
 
     switch (host_impl->active_tree()->source_frame_number()) {
       case 0:
         // Before the layer has a frame to display it should not
         // be visible at all, and not damage anything.
         EXPECT_EQ(gfx::RectF(0.f, 0.f, 0.f, 0.f).ToString(),
                   damage_rect.ToString());
         break;
       case 1:
         EXPECT_EQ(gfx::RectF(0.f, 0.f, 10.f, 10.f).ToString(),
@@ skipping 966 matching lines @@
     }
   }
 
   virtual void AfterTest() OVERRIDE {}
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostDelegatedTestCommitWithoutTake)
 
 }  // namespace
 }  // namespace cc