Add canvas context type histogram

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 6cf7ae93bf0c4a4eefaf2599bee04b57eed575d0..ed183b47684f8c5e1d16e4412843cf24be541822 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1085,6 +1085,12 @@ other types of suffix sets.
   </summary>
 </histogram>
 
+<histogram name="Canvas.ContextType" enum="CanvasContextType">
+  <summary>
+    Records the context type names used to create canvas rendering contexts.
+  </summary>
+</histogram>
+
 <histogram name="Cellular.ActivationFailure">
   <summary>
     The count of cellular device activation failures (Chrome OS).
@@ -15754,6 +15760,13 @@ other types of suffix sets.
   <int value="1" label="Wiped out"/>
 </enum>
 
+<enum name="CanvasContextType" type="int">
+  <int value="0" label="2d"/>
+  <int value="1" label="webkit-3d"/>
+  <int value="2" label="experimental-webgl"/>
+  <int value="3" label="webgl"/>
+</enum>
+
 <enum name="ChannelLayout" type="int">
   <int value="0" label="CHANNEL_LAYOUT_NONE"/>
   <int value="1" label="CHANNEL_LAYOUT_UNSUPPORTED"/>