cc: Introduce CompositorMode enum.

cc/trees/layer_tree_host.h

Index: cc/trees/layer_tree_host.h
diff --git a/cc/trees/layer_tree_host.h b/cc/trees/layer_tree_host.h
index 9c8e1eccb0b3b3dcd9a5bbfdd0c688590e2f8982..3bfd73ca5c9cd4108ee22462b1299c98330b5333 100644
--- a/cc/trees/layer_tree_host.h
+++ b/cc/trees/layer_tree_host.h
@@ -33,6 +33,7 @@
 #include "cc/resources/resource_format.h"
 #include "cc/resources/scoped_ui_resource.h"
 #include "cc/surfaces/surface_sequence.h"
+#include "cc/trees/compositor_mode.h"
 #include "cc/trees/layer_tree_host_client.h"
 #include "cc/trees/layer_tree_host_common.h"
 #include "cc/trees/layer_tree_settings.h"
@@ -359,7 +360,7 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
   bool HasActiveAnimation(const Layer* layer) const;
 
  protected:
-  explicit LayerTreeHost(InitParams* params);
+  LayerTreeHost(InitParams* params, CompositorMode mode);
   void InitializeThreaded(
       scoped_refptr<base::SingleThreadTaskRunner> main_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> impl_task_runner,
@@ -397,6 +398,9 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
 
   bool AnimateLayersRecursive(Layer* current, base::TimeTicks time);
 
+  bool IsSingleThreaded() const;
+  bool IsThreaded() const;
+
   struct UIResourceClientData {
     UIResourceClient* client;
     gfx::Size size;
@@ -417,6 +421,8 @@ class CC_EXPORT LayerTreeHost : public MutatorHostClient {
 
   void SetPropertyTreesNeedRebuild();
 
+  const CompositorMode compositor_mode_;
+
   bool needs_full_tree_sync_;
   bool needs_meta_info_recomputation_;