Add trace event for addition/removal of GPU rasterization trigger

cc/trees/layer_tree_host.cc

Index: cc/trees/layer_tree_host.cc
diff --git a/cc/trees/layer_tree_host.cc b/cc/trees/layer_tree_host.cc
index 5df8fc4ac529125338aad564e79f8ab93e7855aa..ef21f1b57fb9f9997cd66673d276ab0537791205 100644
--- a/cc/trees/layer_tree_host.cc
+++ b/cc/trees/layer_tree_host.cc
@@ -619,6 +619,18 @@ bool LayerTreeHost::UseGpuRasterization() const {
   }
 }
 
+void LayerTreeHost::SetHasGpuRasterizationTrigger(bool has_trigger) {
+  if (has_trigger == has_gpu_rasterization_trigger_)
+    return;
+
+  has_gpu_rasterization_trigger_ = has_trigger;
+  TRACE_EVENT_INSTANT1("cc",
+                       "LayerTreeHost::SetHasGpuRasterizationTrigger",
+                       TRACE_EVENT_SCOPE_THREAD,
+                       "has_trigger",
+                       has_gpu_rasterization_trigger_);
+}
+
 void LayerTreeHost::SetViewportSize(const gfx::Size& device_viewport_size) {
   if (device_viewport_size == device_viewport_size_)
     return;