Add stream operator for SurfaceId/FrameSinkId/LocalFrameId.

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 aa6c9c5d667fe420743e97585f796378b165076f..6df5009a2bd5cce8146cb3d0c391f0ea778337c0 100644
--- a/cc/surfaces/surface_id.h
+++ b/cc/surfaces/surface_id.h
@@ -5,15 +5,13 @@
 #ifndef CC_SURFACES_SURFACE_ID_H_
 #define CC_SURFACES_SURFACE_ID_H_
 
-#include <stddef.h>
 #include <stdint.h>
 
-#include <functional>
+#include <iosfwd>
 #include <string>
 
 #include "base/format_macros.h"
 #include "base/hash.h"
-#include "base/strings/stringprintf.h"
 #include "cc/surfaces/frame_sink_id.h"
 #include "cc/surfaces/local_frame_id.h"
 
@@ -49,11 +47,7 @@ class SurfaceId {
 
   const LocalFrameId& local_frame_id() const { return local_frame_id_; }
 
-  std::string ToString() const {
-    return base::StringPrintf("SurfaceId(%s, %s)",
-                              frame_sink_id_.ToString().c_str(),
-                              local_frame_id_.ToString().c_str());
-  }
+  std::string ToString() const;
 
   bool operator==(const SurfaceId& other) const {
     return frame_sink_id_ == other.frame_sink_id_ &&
@@ -73,6 +67,8 @@ class SurfaceId {
   LocalFrameId local_frame_id_;
 };
 
+std::ostream& operator<<(std::ostream& out, const SurfaceId& surface_id);
+
 struct SurfaceIdHash {
   size_t operator()(const SurfaceId& key) const { return key.hash(); }
 };