Make cc::SurfaceId unguessable

cc/layers/surface_layer_impl.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/surface_layer_impl.h"
 
 #include <stdint.h>
 
 #include "base/trace_event/trace_event_argument.h"
 #include "cc/debug/debug_colors.h"
@@ skipping 161 matching lines @@
       SolidColorDrawQuad* right_quad =
           render_pass->CreateAndAppendDrawQuad<SolidColorDrawQuad>();
       right_quad->SetNew(shared_quad_state, right, right,
                          colors[i % kNumColors], force_anti_aliasing_off);
     }
   }
 }
 
 void SurfaceLayerImpl::AsValueInto(base::trace_event::TracedValue* dict) const {
   LayerImpl::AsValueInto(dict);
-  dict->SetInteger("surface_id", surface_id_.id);
+  dict->SetString("surface_id", surface_id_.ToString());
 }
 
 const char* SurfaceLayerImpl::LayerTypeAsString() const {
   return "cc::SurfaceLayerImpl";
 }
 
 }  // namespace cc