Fix Blink.CompositingCommit.UpdateTime metric

https://crrev.com/580735 updated the wrong Blink.Compositing.UpdateTime
metric due to a rebase mistake. This patch fixes the mistake so that the
following is true:

SPV175 (current):
Only Blink.Compositing.UpdateTime

BlinkGenPropertyTrees:
Blink.CompositingCommit.UpdateTime and Blink.Compositing.UpdateTime

SPV2:
Only Blink.CompositingCommit.UpdateTime

Bug: 865168
Change-Id: I50b3bc45454755ce82ba72da05c42000eca971b7
Reviewed-on: https://chromium-review.googlesource.com/1181647Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584537}

third_party/blink/renderer/core/frame/local_frame_view.cc

@@ -2529,8 +2529,8 @@ bool LocalFrameView::RunCompositingLifecyclePhase(
   DCHECK(layout_view);
 
   if (!RuntimeEnabledFeatures::SlimmingPaintV2Enabled()) {
-    SCOPED_UMA_AND_UKM_TIMER("Blink.CompositingCommit.UpdateTime",
-                             UkmMetricNames::kCompositingCommit);
+    SCOPED_UMA_AND_UKM_TIMER("Blink.Compositing.UpdateTime",
+                             UkmMetricNames::kCompositing);
     layout_view->Compositor()->UpdateIfNeededRecursive(target_state);
   } else {
     ForAllNonThrottledLocalFrameViews([](LocalFrameView& frame_view) {
@@ -2918,8 +2918,8 @@ void LocalFrameView::PushPaintArtifactToCompositor(
         paint_artifact_compositor_->RootLayer(), &GetFrame());
   }
 
-  SCOPED_UMA_AND_UKM_TIMER("Blink.Compositing.UpdateTime",
-                           UkmMetricNames::kCompositing);
+  SCOPED_UMA_AND_UKM_TIMER("Blink.CompositingCommit.UpdateTime",
+                           UkmMetricNames::kCompositingCommit);
 
   paint_artifact_compositor_->Update(
       paint_controller_->GetPaintArtifactShared(), composited_element_ids,