cc: Make PrepareToDraw return an enum for why it aborts

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 <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 691 matching lines @@
         break;
       case 19:
         // Set another new frame, both layers should be damaged in the same
         // ways.
         SetFrameData(
             CreateFrameData(gfx::Rect(0, 0, 10, 10), gfx::Rect(3, 3, 1, 1)));
     }
     first_draw_for_source_frame_ = true;
   }
 
-  virtual bool PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
-                                     LayerTreeHostImpl::FrameData* frame,
-                                     bool result) OVERRIDE {
-    EXPECT_TRUE(result);
+  virtual DrawSwapReadbackResult::DrawResult PrepareToDrawOnThread(
+      LayerTreeHostImpl* host_impl,
+      LayerTreeHostImpl::FrameData* frame,
+      DrawSwapReadbackResult::DrawResult draw_result) OVERRIDE {
+    EXPECT_EQ(DrawSwapReadbackResult::DRAW_SUCCESS, draw_result);
 
     if (!first_draw_for_source_frame_)
-      return result;
+      return draw_result;
 
     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()) {
@@ skipping 75 matching lines @@
                                   gfx::RectF(4.f, 0.f, 1.f, 1.f)).ToString(),
                   damage_rect.ToString());
         break;
       case 19:
         EXPECT_EQ(gfx::RectF(3.f, 3.f, 6.f, 1.f).ToString(),
                   damage_rect.ToString());
         EndTest();
         break;
     }
 
-    return result;
+    return draw_result;
   }
 
  protected:
   scoped_refptr<DelegatedRendererLayer> delegated_copy_;
   bool first_draw_for_source_frame_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostDelegatedTestLayerUsesFrameDamage);
 
 class LayerTreeHostDelegatedTestMergeResources
@@ skipping 1509 matching lines @@
   }
 
   scoped_refptr<DelegatedRendererLayer> delegated_thief_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(
     LayerTreeHostDelegatedTestRemoveAndChangeResources);
 
 }  // namespace
 }  // namespace cc