Track performance of toBlob and its complete timeout delay

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 28d90ca0cba04971f8185933e98c46b9baf60fd6..0c84e865fc1104ac0e2a6e1e5a32f6a374d1dfa7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -3478,6 +3478,16 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <summary>Time spent on 2D canvas putImageData API call.</summary>
 </histogram>
 
+<histogram name="Blink.Canvas.ToBlob" units="microseconds">
+  <owner>junov@chromium.org</owner>
+  <summary>Time spent on 2D canvas toBlob API call.</summary>
+</histogram>
+
+<histogram name="Blink.Canvas.ToBlobTimeoutDuration" units="microseconds">
+  <owner>xlai@chromium.org</owner>
+  <summary>Duration of a timeout event in a canvas.toBlob API call.</summary>
+</histogram>
+
 <histogram name="Blink.Canvas.ToDataURL" units="microseconds">
   <owner>junov@chromium.org</owner>
   <summary>Time spent on 2D canvas toDataURL API call.</summary>
@@ -4336,6 +4346,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Canvas.ToBlob.IdleTaskTimeoutSwitch"
+    enum="IdleTaskTimeoutType">
+  <owner>xlai@chromium.org</owner>
+  <summary>
+    Records the occurence of start/complete time out delay in canvas toBlob
+    calls.
+  </summary>
+</histogram>
+
 <histogram name="CAPSUpdater.Step" enum="CAPSUpdaterStep">
   <owner>cpu@chromium.org</owner>
   <summary>
@@ -76907,6 +76926,11 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </int>
 </enum>
 
+<enum name="IdleTaskTimeoutType" type="int">
+  <int value="0" label="IdleTaskStartTimeout"/>
+  <int value="2" label="IdleTaskCompleteTimeout"/>
+</enum>
+
 <enum name="IMECommitType" type="int">
   <obsolete>
     Deprecated 03/2015, and replaced by IMECommitType2.
@@ -91876,6 +91900,28 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Blink.Canvas.PutImageData"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="BlinkCanvasToBlobTimeoutTimer" separator=".">
+  <suffix name="Start"/>
+  <suffix name="Complete"/>

[Ilya Sherman, 2016/06/08 04:14:35]

I don't understand what it means to start vs. complete a timeout.  If this is an
important distinction to measure, could you please clarify within the
description text in this file what each of these cases means?

+  <affected-histogram name="Blink.Canvas.ToBlobTimeoutDuration.JPEG"/>
+  <affected-histogram name="Blink.Canvas.ToBlobTimeoutDuration.PNG"/>
+  <affected-histogram name="Blink.Canvas.ToBlobTimeoutDuration.WEBP"/>
+</histogram_suffixes>
+
+<histogram_suffixes name="BlinkCanvasToBlobTimeoutType" separator=".">
+  <suffix name="JPEG"/>
+  <suffix name="PNG"/>
+  <suffix name="WEBP"/>
+  <affected-histogram name="Blink.Canvas.ToBlobTimeoutDuration"/>
+</histogram_suffixes>
+
+<histogram_suffixes name="BlinkCanvasToBlobType" separator=".">
+  <suffix name="JPEG"/>
+  <suffix name="PNG"/>
+  <suffix name="WEBP"/>
+  <affected-histogram name="Blink.Canvas.ToBlob"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="BlinkCanvasToDataURLTime" separator=".">
   <suffix name="BMP"/>
   <suffix name="GIF"/>
@@ -92088,6 +92134,12 @@ To add a new entry, add it with any value and run test to compute valid value.
   <affected-histogram name="Canvas.RequestedImageMimeTypes"/>
 </histogram_suffixes>
 
+<histogram_suffixes name="CanvasToBlobIdleTaskTimeoutSwitch" separator=".">
+  <suffix name="PNG"/>
+  <suffix name="JPEG"/>
+  <affected-histogram name="Canvas.ToBlob.IdleTaskTimeoutSwitch"/>
+</histogram_suffixes>
+
 <histogram_suffixes name="CertificateTypeAlgorithms" separator=".">
   <owner>rsleevi@chromium.org</owner>
   <suffix name="DH" label="DH"/>