cc: Add UMA stats for record and raster time.

cc/resources/display_list_recording_source.cc

Index: cc/resources/display_list_recording_source.cc
diff --git a/cc/resources/display_list_recording_source.cc b/cc/resources/display_list_recording_source.cc
index 3a47c9067ca4dc7e0634aca8269100887a91a304..f8e26dc19c5c7542e04ec991ec7b69841da44404 100644
--- a/cc/resources/display_list_recording_source.cc
+++ b/cc/resources/display_list_recording_source.cc
@@ -6,6 +6,7 @@
 
 #include <algorithm>
 
+#include "cc/base/histograms.h"
 #include "cc/base/region.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/resources/display_item_list.h"
@@ -22,6 +23,11 @@ const int kPixelDistanceToRecord = 8000;
 // operations.
 const int kOpCountThatIsOkToAnalyze = 10;
 
+DEFINE_SCOPED_UMA_HISTOGRAM_AREA_TIMER(
+    ScopedDisplayListRecordingSourceUpdateTimer,
+    "Renderer4.DisplayListRecordingSourceRecordUs",
+    "Renderer4.DisplayListRecordingSourceRecordedAreaPerMs");
+
 }  // namespace
 
 namespace cc {
@@ -49,6 +55,7 @@ bool DisplayListRecordingSource::UpdateAndExpandInvalidation(
     const gfx::Rect& visible_layer_rect,
     int frame_number,
     RecordingMode recording_mode) {
+  ScopedDisplayListRecordingSourceUpdateTimer timer;
   bool updated = false;
 
   if (size_ != layer_size) {
@@ -74,6 +81,10 @@ bool DisplayListRecordingSource::UpdateAndExpandInvalidation(
     updated = true;
   }
 
+  // Count the area that is being invalidated.
+  for (Region::Iterator it(*invalidation); it.has_rect(); it.next())

[enne (OOO), 2015/04/13 21:52:26]

This is a petty nit, but it's weird to have this inside the timer.  I think you
could get away with the timer having area as a ctor arg and no Set/Add area
calls.

[jbroman, 2015/04/14 14:44:36]

Prevents the work before the invalidation is available (e.g. in
PicturePile::ApplyInvalidationAndResize) from being counted in the time. (Less
of a big deal now that the invalidation rects, which are available earlier, are
being used.)

Happy to make this change if that tradeoff sgty.

[enne (OOO), 2015/04/14 16:54:10]

Hmm, ok, this is fine.  I am not sure whether it makes sense to include the
synthetic invalidations here, but I think that's ok.  I suspect the display
lists are going to need the same synthetic invalidations for resizing anyway, so
maybe it'll balanceo ut.

+    timer.AddArea(it.rect().size().GetArea());
+
   if (!updated && !invalidation->Intersects(recorded_viewport_))
     return false;