Align base::hash_map with C++11.

cc/trees/layer_sorter.h

Index: cc/trees/layer_sorter.h
diff --git a/cc/trees/layer_sorter.h b/cc/trees/layer_sorter.h
index c5aab7ca780a59807f04dfd2e0e208ecac86c9a7..7dd980ce947feb47311acf1e65b640b7950d44ba 100644
--- a/cc/trees/layer_sorter.h
+++ b/cc/trees/layer_sorter.h
@@ -16,19 +16,6 @@
 #include "ui/gfx/rect_f.h"
 #include "ui/gfx/vector3d_f.h"
 
-#if defined(COMPILER_GCC)
-namespace cc { struct GraphEdge; }
-
-namespace BASE_HASH_NAMESPACE {
-template <>
-struct hash<cc::GraphEdge*> {
-  size_t operator()(cc::GraphEdge* ptr) const {
-    return hash<size_t>()(reinterpret_cast<size_t>(ptr));
-  }
-};
-}  // namespace BASE_HASH_NAMESPACE
-#endif  // COMPILER
-
 namespace gfx {
 class Transform;
 }