Add UMA metrics to OffscreenCanvas's commit type

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 dab2823baf130f8be11bd6d15a2c50a909b7456a..05a932ef8c5051e2ca6b91060c8259135a56ccd0 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -4995,6 +4995,14 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="Canvas.Offscreen.CommitType" enum="OffscreenCanvasCommitType">
+  <owner>xidachen@chromium.org</owner>
+  <owner>junov@chromium.org</owner>
+  <summary>
+    The type of code path that OffscreenCanvas's commit API goes through.
+  </summary>
+</histogram>
+
 <histogram name="Canvas.RequestedImageMimeTypes" enum="RequestedImageMimeType">
   <owner>xlai@chromium.org</owner>
   <summary>
@@ -92030,6 +92038,13 @@ value.
   <int value="4" label="Server offline and stale data not available."/>
 </enum>
 
+<enum name="OffscreenCanvasCommitType" type="int">
+  <int value="0" label="GPUCanvasGPUCompositing"/>
+  <int value="1" label="GPUCanvasSoftwareCompositing"/>
+  <int value="2" label="SoftwareCanvasGPUCompositing"/>
+  <int value="3" label="SoftwareCanvasSoftwareCompositing"/>
+</enum>
+
 <enum name="OmniboxAggressiveHistoryURLProviderFieldTrialBeacon" type="int">
   <int value="0" label="disabled by flags"/>
   <int value="1" label="enabled by flags"/>