Add cc::Surface ref counting.

cc/surfaces/surface_id.h

Index: cc/surfaces/surface_id.h
diff --git a/cc/surfaces/surface_id.h b/cc/surfaces/surface_id.h
index 5be370ed3fb427249f2ec9b6428bb37984eedbce..247111e8ca39746ff791809c77367b72182ecd81 100644
--- a/cc/surfaces/surface_id.h
+++ b/cc/surfaces/surface_id.h
@@ -9,6 +9,7 @@
 #include <stdint.h>
 
 #include <functional>
+#include <string>
 
 #include "base/format_macros.h"
 #include "base/hash.h"
@@ -20,9 +21,9 @@ namespace cc {
 
 class SurfaceId {
  public:
-  SurfaceId() = default;
+  constexpr SurfaceId() = default;
 
-  SurfaceId(const SurfaceId& other)
+  constexpr SurfaceId(const SurfaceId& other)

[vmpstr, 2016/11/02 20:28:12]

Can this also be = default?

[kylechar, 2016/11/02 21:21:20]

Done.

       : frame_sink_id_(other.frame_sink_id_),
         local_frame_id_(other.local_frame_id_) {}
 
@@ -37,8 +38,8 @@ class SurfaceId {
   // impossible for an unprivileged frame source to embed another frame source
   // without being explicitly given the surface ID of that frame source from a
   // privileged process.
-  SurfaceId(const FrameSinkId& frame_sink_id,
-            const LocalFrameId& local_frame_id)
+  constexpr SurfaceId(const FrameSinkId& frame_sink_id,
+                      const LocalFrameId& local_frame_id)
       : frame_sink_id_(frame_sink_id), local_frame_id_(local_frame_id) {}
 
   bool is_null() const {