Implement scroll handler latency tracking

cc/trees/layer_tree_host_impl_unittest.cc

Index: cc/trees/layer_tree_host_impl_unittest.cc
diff --git a/cc/trees/layer_tree_host_impl_unittest.cc b/cc/trees/layer_tree_host_impl_unittest.cc
index 0f396803400483af3f29e14d6a4d7dae1305d505..c944b67fff17e0b907a3ba03b88fb7632ea670aa 100644
--- a/cc/trees/layer_tree_host_impl_unittest.cc
+++ b/cc/trees/layer_tree_host_impl_unittest.cc
@@ -972,6 +972,24 @@ TEST_F(LayerTreeHostImplTest, ImplPinchZoom) {
   }
 }
 
+TEST_F(LayerTreeHostImplTest, ScrollWithSwapPromises) {
+  ui::LatencyInfo latency_info;
+  latency_info.trace_id = 1234;
+  scoped_ptr<SwapPromise> swap_promise(
+      new LatencyInfoSwapPromise(latency_info));
+
+  SetupScrollAndContentsLayers(gfx::Size(100, 100));
+  EXPECT_EQ(InputHandler::ScrollStarted,
+            host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
+  host_impl_->ScrollBy(gfx::Point(), gfx::Vector2d(0, 10));
+  host_impl_->QueueSwapPromiseForMainThreadScrollUpdate(swap_promise.Pass());
+  host_impl_->ScrollEnd();
+
+  scoped_ptr<ScrollAndScaleSet> scroll_info = host_impl_->ProcessScrollDeltas();
+  EXPECT_EQ(1u, scroll_info->swap_promises.size());
+  EXPECT_EQ(latency_info.trace_id, scroll_info->swap_promises[0]->TraceId());
+}
+
 TEST_F(LayerTreeHostImplTest, MasksToBoundsDoesntClobberInnerContainerSize) {
   SetupScrollAndContentsLayers(gfx::Size(100, 100));
   host_impl_->SetViewportSize(gfx::Size(50, 50));
@@ -6362,10 +6380,12 @@ class SimpleSwapPromiseMonitor : public SwapPromiseMonitor {
   SimpleSwapPromiseMonitor(LayerTreeHost* layer_tree_host,
                            LayerTreeHostImpl* layer_tree_host_impl,
                            int* set_needs_commit_count,
-                           int* set_needs_redraw_count)
+                           int* set_needs_redraw_count,
+                           int* forward_to_main_count)
       : SwapPromiseMonitor(layer_tree_host, layer_tree_host_impl),
         set_needs_commit_count_(set_needs_commit_count),
-        set_needs_redraw_count_(set_needs_redraw_count) {}
+        set_needs_redraw_count_(set_needs_redraw_count),
+        forward_to_main_count_(forward_to_main_count) {}
 
   virtual ~SimpleSwapPromiseMonitor() {}
 
@@ -6377,24 +6397,32 @@ class SimpleSwapPromiseMonitor : public SwapPromiseMonitor {
     (*set_needs_redraw_count_)++;
   }
 
+  virtual void OnForwardScrollUpdateToMainThreadOnImpl() OVERRIDE {
+    (*forward_to_main_count_)++;
+  }
+
  private:
   int* set_needs_commit_count_;
   int* set_needs_redraw_count_;
+  int* forward_to_main_count_;
 };
 
 TEST_F(LayerTreeHostImplTest, SimpleSwapPromiseMonitor) {
   int set_needs_commit_count = 0;
   int set_needs_redraw_count = 0;
+  int forward_to_main_count = 0;
 
   {
     scoped_ptr<SimpleSwapPromiseMonitor> swap_promise_monitor(
         new SimpleSwapPromiseMonitor(NULL,
                                      host_impl_.get(),
                                      &set_needs_commit_count,
-                                     &set_needs_redraw_count));
+                                     &set_needs_redraw_count,
+                                     &forward_to_main_count));
     host_impl_->SetNeedsRedraw();
     EXPECT_EQ(0, set_needs_commit_count);
     EXPECT_EQ(1, set_needs_redraw_count);
+    EXPECT_EQ(0, forward_to_main_count);
   }
 
   // Now the monitor is destroyed, SetNeedsRedraw() is no longer being
@@ -6402,16 +6430,19 @@ TEST_F(LayerTreeHostImplTest, SimpleSwapPromiseMonitor) {
   host_impl_->SetNeedsRedraw();
   EXPECT_EQ(0, set_needs_commit_count);
   EXPECT_EQ(1, set_needs_redraw_count);
+  EXPECT_EQ(0, forward_to_main_count);
 
   {
     scoped_ptr<SimpleSwapPromiseMonitor> swap_promise_monitor(
         new SimpleSwapPromiseMonitor(NULL,
                                      host_impl_.get(),
                                      &set_needs_commit_count,
-                                     &set_needs_redraw_count));
+                                     &set_needs_redraw_count,
+                                     &forward_to_main_count));
     host_impl_->SetNeedsRedrawRect(gfx::Rect(10, 10));
     EXPECT_EQ(0, set_needs_commit_count);
     EXPECT_EQ(2, set_needs_redraw_count);
+    EXPECT_EQ(0, forward_to_main_count);
   }
 
   {
@@ -6419,11 +6450,48 @@ TEST_F(LayerTreeHostImplTest, SimpleSwapPromiseMonitor) {
         new SimpleSwapPromiseMonitor(NULL,
                                      host_impl_.get(),
                                      &set_needs_commit_count,
-                                     &set_needs_redraw_count));
+                                     &set_needs_redraw_count,
+                                     &forward_to_main_count));
     // Empty damage rect won't signal the monitor.
     host_impl_->SetNeedsRedrawRect(gfx::Rect());
     EXPECT_EQ(0, set_needs_commit_count);
     EXPECT_EQ(2, set_needs_redraw_count);
+    EXPECT_EQ(0, forward_to_main_count);
+  }
+
+  {
+    set_needs_commit_count = 0;
+    set_needs_redraw_count = 0;
+    forward_to_main_count = 0;
+    scoped_ptr<SimpleSwapPromiseMonitor> swap_promise_monitor(
+        new SimpleSwapPromiseMonitor(NULL,
+                                     host_impl_.get(),
+                                     &set_needs_commit_count,
+                                     &set_needs_redraw_count,
+                                     &forward_to_main_count));
+    LayerImpl* scroll_layer = SetupScrollAndContentsLayers(gfx::Size(100, 100));
+
+    // Scrolling normally should not trigger any forwarding.
+    EXPECT_EQ(InputHandler::ScrollStarted,
+              host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
+    EXPECT_TRUE(host_impl_->ScrollBy(gfx::Point(), gfx::Vector2d(0, 10)));
+    host_impl_->ScrollEnd();
+
+    EXPECT_EQ(0, set_needs_commit_count);
+    EXPECT_EQ(1, set_needs_redraw_count);
+    EXPECT_EQ(0, forward_to_main_count);
+
+    // Scrolling with a scroll handler should defer the swap to the main
+    // thread.
+    scroll_layer->SetHaveScrollEventHandlers(true);
+    EXPECT_EQ(InputHandler::ScrollStarted,
+              host_impl_->ScrollBegin(gfx::Point(), InputHandler::Gesture));
+    EXPECT_TRUE(host_impl_->ScrollBy(gfx::Point(), gfx::Vector2d(0, 10)));
+    host_impl_->ScrollEnd();
+
+    EXPECT_EQ(0, set_needs_commit_count);
+    EXPECT_EQ(2, set_needs_redraw_count);
+    EXPECT_EQ(1, forward_to_main_count);
   }
 }