Fix UMA histogram name in DrmOverlayManager

In my previous CL, I updated the name in histograms.xml but I forgot to
actually change the code.

Change-Id: Ie7eb42a0303d9c98d46a2a1dff126dfd498a719f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1954300
Auto-Submit: Saman Sami <samans@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Commit-Queue: Saman Sami <samans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#722471}

ui/ozone/platform/drm/common/drm_overlay_manager.cc

@@ -104,7 +104,8 @@ void DrmOverlayManager::CheckOverlaySupport(
       candidates->at(i).overlay_handled = status[i] == OVERLAY_STATUS_ABLE;
     }
   }
-  UMA_HISTOGRAM_BOOLEAN("DrmOverlayManager.CacheHit", cache_hit);
+  UMA_HISTOGRAM_BOOLEAN("Compositing.Display.DrmOverlayManager.CacheHit",
+                        cache_hit);
 }
 
 bool DrmOverlayManager::CanHandleCandidate(