Replaced cc::SurfaceId::nonce_ with base::UnguessableToken

cc/surfaces/surface_id.h

 // 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.
 
 #ifndef CC_SURFACES_SURFACE_ID_H_
 #define CC_SURFACES_SURFACE_ID_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <functional>
 #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"
 
 namespace cc {
 
 class SurfaceId {
  public:
   constexpr SurfaceId() = default;
 
   constexpr SurfaceId(const SurfaceId& other) = default;
 
-  // A SurfaceId consists of three components: FrameSinkId, local Id, and nonce.
+  // A SurfaceId consists of two components: FrameSinkId and LocalFrameId.
   // A |frame_sink_id| consists of two components; one is allocated by the
   // display compositor service and one is allocated by the client. The
   // |frame_sink_id| uniquely identifies a FrameSink (and frame source).
-  // A |local_id| is a sequentially allocated ID generated by the frame source
-  // that uniquely identifies a sequential set of frames of the same size and
-  // device scale factor.
-  // A |nonce| is a cryptographically secure unguessable token that makes it
-  // 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.
+  // A |local_frame_id| is a sequentially allocated ID generated by the frame
+  // source that uniquely identifies a sequential set of frames of the same size
+  // and device scale factor.
   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_valid() const {
     return frame_sink_id_.is_valid() && local_frame_id_.is_valid();
   }
 
   size_t hash() const {
     return base::HashInts(static_cast<uint64_t>(frame_sink_id_.hash()),
@@ skipping 28 matching lines @@
   LocalFrameId local_frame_id_;
 };
 
 struct SurfaceIdHash {
   size_t operator()(const SurfaceId& key) const { return key.hash(); }
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_ID_H_