Estimate draw duration in SchedulerClient

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 8591 matching lines @@
 </histogram>
 
 <histogram name="Profile.CreateTimeCanceled" units="milliseconds">
   <summary>
     Time elapsed before the user decided to cancel creation of a new profile.
     Since only managed-user profile creation can be canceled, this time comes
     from managed-user registration.
   </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
     promoting all layers that have a webkit-transition on opacity or transform.
   </summary>
 </histogram>
 
 <histogram name="Renderer2.FinishDocToFinish">
   <summary>
     The time from when a document finished loading to when all it's resources
@@ skipping 9563 matching lines @@
   <group name="Disabled" label="Neither extra webstore link is visible"/>
   <group name="FooterLink" label="Link in bottom right of footer"/>
   <group name="PlusIcon" label="Plus icon in apps page"/>
   <affected-histogram name="Extensions.AppLaunch"/>
   <affected-histogram name="NewTabPage.DefaultPageType"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>