Port rendering_stats' implementation to javascript

tracing/tracing/extras/chrome/cc/constants.html

Index: tracing/tracing/extras/chrome/cc/constants.html
diff --git a/tracing/tracing/extras/chrome/cc/constants.html b/tracing/tracing/extras/chrome/cc/constants.html
index c65adca5b593962d8a524897b67fc33c4315e9de..d7580e558840ed0a21c9b1b1deba1e1ec19be814 100644
--- a/tracing/tracing/extras/chrome/cc/constants.html
+++ b/tracing/tracing/extras/chrome/cc/constants.html
@@ -20,6 +20,50 @@ tr.exportTo('tr.e.cc', function() {
     'ThreadProxy::ScheduledActionSendBeginMainFrame';
   constants.BEGIN_MAIN_FRAME_EVENT = 'ThreadProxy::BeginMainFrame';
 
+  // These are LatencyInfo component names indicating the various components
+  // that the input event has travelled through.
+  // This is when the input event first reaches chrome.
+  constants.UI_COMP_NAME = 'INPUT_EVENT_LATENCY_UI_COMPONENT';
+
+  // This is when the input event was originally created by OS.
+  constants.ORIGINAL_COMP_NAME = 'INPUT_EVENT_LATENCY_ORIGINAL_COMPONENT';
+
+  // This is when the input event was sent from browser to renderer.
+  constants.BEGIN_COMP_NAME = 'INPUT_EVENT_LATENCY_BEGIN_RWH_COMPONENT';
+
+  // This is when an input event is turned into a scroll update.
+  constants.BEGIN_SCROLL_UPDATE_COMP_NAME = (
+    'LATENCY_BEGIN_SCROLL_LISTENER_UPDATE_MAIN_COMPONENT');
+
+  // This is when a scroll update is forwarded to the main thread.
+  constants.FORWARD_SCROLL_UPDATE_COMP_NAME = (
+    'INPUT_EVENT_LATENCY_FORWARD_SCROLL_UPDATE_TO_MAIN_COMPONENT');
+
+  // This is when the input event has reached swap buffer.
+  constants.END_COMP_NAME = 'INPUT_EVENT_GPU_SWAP_BUFFER_COMPONENT';
+
+  // Name for a main thread scroll update latency event.
+  constants.SCROLL_UPDATE_EVENT_NAME = 'Latency::ScrollUpdate';
+  // Name for a gesture scroll update latency event.
+  constants.GESTURE_SCROLL_UPDATE_EVENT_NAME =
+    'InputLatency::GestureScrollUpdate';
+
+  // These are keys used in the 'data' field dictionary located in
+  // BenchmarkInstrumentation::ImplThreadRenderingStats.
+  constants.VISIBLE_CONTENT_DATA = 'visible_content_area';
+  constants.APPROXIMATED_VISIBLE_CONTENT_DATA =
+    'approximated_visible_content_area';
+  constants.CHECKERBOARDED_VISIBLE_CONTENT_DATA =
+    'checkerboarded_visible_content_area';
+
+  constants.BENCHMARK_DISPLAY_RENDERING_STATS =
+    'BenchmarkInstrumentation::DisplayRenderingStats';
+
+  constants.BENCHMARK_IMPL_THREAD_RENDERING_STATS =
+    'BenchmarkInstrumentation::ImplThreadRenderingStats';
+
+  constants.VSYNC_BEFORE = 'vsync_before';
+
   return {
     constants: constants
   };