Estimate draw duration in SchedulerClient

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 963bb406482ddfc58592ebedcacac87c7eb5a0e2..87bb88db41cd7530ffac53b013a373ba26b57b79 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8609,6 +8609,24 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Renderer.DrawDuration" units="milliseconds">
+  <summary>The time it takes for the compositor to draw a frame.</summary>
+</histogram>
+
+<histogram name="Renderer.DrawDurationOverestimate" units="milliseconds">
+  <summary>
+    The amout by which the compositor's draw duration was overestimated in a

[jar (doing other things), 2013/06/12 19:09:38]

amout-->amount

[ajuma, 2013/06/12 19:28:52]

Fixed.

+    particular frame.
+  </summary>
+</histogram>
+
+<histogram name="Renderer.DrawDurationUnderestimate" units="milliseconds">
+  <summary>
+    The amount by which the compositor's draw duration was underestimated in a

[jar (doing other things), 2013/06/12 19:09:38]

Can you also explain when a sample is added?  For instance, do you always add a
sample to at least 2 out of 3 of these... and when the prediction is perfect...
do you add a sample to all 3??

[ajuma, 2013/06/12 19:28:52]

We always add a sample to all 3 (e.g. adding a sample of 0 to
DrawDurationUnderestimate when the prediction is perfect or actually an
overestimate). I've updated the descriptions.

+    particular frame.
+  </summary>
+</histogram>
+
 <histogram name="Renderer.PixelIncreaseFromTransitions">
   <summary>
     A lower-bound on the percentage increase in memory that would result from