Move LayerTreeHostImpl::SetVisible trace to "cc" from "webkit".

Long live cc.

R=enne, vmpstr

Review URL: https://codereview.chromium.org/897873005

Cr-Commit-Position: refs/heads/master@{#314684}

cc/trees/layer_tree_host_impl.cc

@@ -119,15 +119,12 @@ class ViewportAnchor {
 
 void DidVisibilityChange(LayerTreeHostImpl* id, bool visible) {
   if (visible) {
-    TRACE_EVENT_ASYNC_BEGIN1("webkit",
-                             "LayerTreeHostImpl::SetVisible",
-                             id,
-                             "LayerTreeHostImpl",
-                             id);
+    TRACE_EVENT_ASYNC_BEGIN1("cc", "LayerTreeHostImpl::SetVisible", id,
+                             "LayerTreeHostImpl", id);
     return;
   }
 
-  TRACE_EVENT_ASYNC_END0("webkit", "LayerTreeHostImpl::SetVisible", id);
+  TRACE_EVENT_ASYNC_END0("cc", "LayerTreeHostImpl::SetVisible", id);
 }
 
 size_t GetMaxTransferBufferUsageBytes(