Move RenderStats enumeration out of gpu_benchmarking_extension.

cc/rendering_stats.h

Index: cc/rendering_stats.h
diff --git a/cc/rendering_stats.h b/cc/rendering_stats.h
index d26cc805256efcc64f781dd27e5ab9e0f4f80e2b..61112504e3756094aba2a9054fe589949247c34c 100644
--- a/cc/rendering_stats.h
+++ b/cc/rendering_stats.h
@@ -6,6 +6,7 @@
 #define CC_RENDERING_STATS_H_
 
 #include "base/basictypes.h"
+#include "base/time.h"
 #include "cc/cc_export.h"
 
 namespace cc {
@@ -24,8 +25,29 @@ struct CC_EXPORT RenderingStats {
     int64 numImplThreadScrolls;
     int64 numMainThreadScrolls;
     int64 numLayersDrawn;
+    // Note: when adding new members, please remember to update enumerateFields
+    // in rendering_stats.cc.
 
     RenderingStats();
+
+    // In conjunction with enumerateFields, this allows the embedder to
+    // enumerate the values in this structure without
+    // having to embed references to its specific member variables. This
+    // simplifies the addition of new fields to this type.
+    class Enumerator {
+    public:
+        virtual void AddInt64(const char* name, int64 value) = 0;
+        virtual void AddDouble(const char* name, double value) = 0;
+        virtual void AddInt(const char* name, int value) = 0;
+        virtual void AddTimeDeltaInSecondsF(const char* name,
+                                            const base::TimeDelta& value) = 0;
+
+    protected:
+        virtual ~Enumerator() { }
+    };
+
+    // Outputs the fields in this structure to the provided enumerator.
+    void EnumerateFields(Enumerator* enumerator) const;
 };
 
 }  // namespace cc