Add enumeration tags to clientRenderingAPI metrics

The newly added clientRenderingAPI metrics is missing from ukm dashboard
Adding <enumeration/> tag should fix the issue.

Bug: 1147230
Change-Id: Ia9ee0ec673fec3db8daaacbdc6fa1ff1558fa121
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2527565Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Commit-Queue: Shrek Shao <shrekshao@google.com>
Cr-Commit-Position: refs/heads/master@{#825884}

tools/metrics/ukm/ukm.xml

@@ -3307,6 +3307,13 @@ be describing additional metrics about the same event.
     <summary>
       Type of rendering context created for HTMLCanvasElement.
     </summary>
+    <aggregation>
+      <history>
+        <statistics>
+          <enumeration/>
+        </statistics>
+      </history>
+    </aggregation>
   </metric>
   <metric name="GPUDevice">
     <summary>
@@ -3317,6 +3324,13 @@ be describing additional metrics about the same event.
     <summary>
       Type of rendering context created for OffscreenCanvas.
     </summary>
+    <aggregation>
+      <history>
+        <statistics>
+          <enumeration/>
+        </statistics>
+      </history>
+    </aggregation>
   </metric>
 </event>