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

cc/trees/layer_tree_host_perftest.cc

Index: cc/trees/layer_tree_host_perftest.cc
diff --git a/cc/trees/layer_tree_host_perftest.cc b/cc/trees/layer_tree_host_perftest.cc
index bd3849e57fae5b360d5b29e0d03a78495c0aa456..8f247e8f3d88f3ab56c6db25eda7738534302a53 100644
--- a/cc/trees/layer_tree_host_perftest.cc
+++ b/cc/trees/layer_tree_host_perftest.cc
@@ -26,7 +26,8 @@ static const int kTimeCheckInterval = 10;
 class LayerTreeHostPerfTest : public LayerTreeTest {
  public:
   LayerTreeHostPerfTest()
-      : num_draws_(0) {
+      : num_draws_(0),
+        full_damage_each_frame_(false) {
     fake_content_layer_client_.set_paint_all_opaque(true);
   }
 
@@ -49,6 +50,8 @@ class LayerTreeHostPerfTest : public LayerTreeTest {
       }
     }
     impl->setNeedsRedraw();
+    if (full_damage_each_frame_)
+      impl->SetFullRootLayerDamage();
   }
 
   virtual void BuildTree() {}
@@ -66,6 +69,7 @@ class LayerTreeHostPerfTest : public LayerTreeTest {
   std::string test_name_;
   base::TimeDelta elapsed_;
   FakeContentLayerClient fake_content_layer_client_;
+  bool full_damage_each_frame_;
 };
 
 
@@ -102,6 +106,14 @@ TEST_F(LayerTreeHostPerfTestJsonReader, TenTenSingleThread) {
   RunTest(false);
 }
 
+// Simulates a tab switcher scene with two stacks of 10 tabs each.
+TEST_F(LayerTreeHostPerfTestJsonReader,
+       TenTenSingleThread_FullDamageEachFrame) {
+  full_damage_each_frame_ = true;
+  ReadTestFile("10_10_layer_tree");
+  RunTest(false);
+}
+
 // Simulates main-thread scrolling on each frame.
 class ScrollingLayerTreePerfTest : public LayerTreeHostPerfTestJsonReader {
  public: