Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

cc/layer_tree_host_common.cc

Index: cc/layer_tree_host_common.cc
diff --git a/cc/layer_tree_host_common.cc b/cc/layer_tree_host_common.cc
index 3d06aa4a12b98233ed420ff14677606e16c3c93e..a728ddb423c9d719b2b8e255625c3b034845414a 100644
--- a/cc/layer_tree_host_common.cc
+++ b/cc/layer_tree_host_common.cc
@@ -286,7 +286,8 @@ static bool subtreeShouldRenderToSeparateSurface(LayerType* layer, bool axisAlig
     // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but it is
     // treated as a 3D object by its parent (i.e. parent does preserve-3d).
     if (layerIsInExisting3DRenderingContext(layer) && !layer->preserves3D() && numDescendantsThatDrawContent > 0) {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface flattening");
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface flattening",
+                             TRACE_EVENT_SCOPE_THREAD);
         return true;
     }
 
@@ -294,7 +295,8 @@ static bool subtreeShouldRenderToSeparateSurface(LayerType* layer, bool axisAlig
     bool layerClipsExternalContent = layerClipsSubtree(layer) || layer->hasDelegatedContent();
     if (layerClipsExternalContent && !axisAlignedWithRespectToParent && !layer->drawProperties().descendants_can_clip_selves)
     {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface clipping");
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface clipping",
+                             TRACE_EVENT_SCOPE_THREAD);
         return true;
     }
 
@@ -306,7 +308,8 @@ static bool subtreeShouldRenderToSeparateSurface(LayerType* layer, bool axisAlig
     bool atLeastTwoLayersInSubtreeDrawContent = numDescendantsThatDrawContent > 0 && (layer->drawsContent() || numDescendantsThatDrawContent > 1);
 
     if (layer->opacity() != 1 && !layer->preserves3D() && atLeastTwoLayersInSubtreeDrawContent) {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface opacity");
+        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface opacity",
+                             TRACE_EVENT_SCOPE_THREAD);
         return true;
     }