FrameSinkIds use to WindowIds in window server, Process ID/Route ID in renderer

third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h

 // Copyright 2015 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 OffscreenCanvas_h
 #define OffscreenCanvas_h
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/ScriptWrappable.h"
@@ skipping 45 matching lines @@
   static void registerRenderingContextFactory(
       std::unique_ptr<CanvasRenderingContextFactory>);
 
   bool originClean() const;
   void setOriginTainted() { m_originClean = false; }
   // TODO(crbug.com/630356): apply the flag to WebGL context as well
   void setDisableReadingFromCanvasTrue() { m_disableReadingFromCanvas = true; }
 
   OffscreenCanvasFrameDispatcher* getOrCreateFrameDispatcher();
 
-  void setSurfaceId(uint32_t clientId, uint32_t localId, uint64_t nonce) {
+  void setSurfaceId(uint32_t clientId,
+                    uint32_t sinkId,
+                    uint32_t localId,
+                    uint64_t nonce) {
     m_clientId = clientId;
+    m_sinkId = sinkId;
     m_localId = localId;
     m_nonce = nonce;
   }
   uint32_t clientId() const { return m_clientId; }
+  uint32_t sinkId() const { return m_sinkId; }
   uint32_t localId() const { return m_localId; }
   uint64_t nonce() const { return m_nonce; }
 
   // CanvasImageSource implementation
   PassRefPtr<Image> getSourceImageForCanvas(SourceImageStatus*,
                                             AccelerationHint,
                                             SnapshotReason,
                                             const FloatSize&) const final;
   bool wouldTaintOrigin(SecurityOrigin*) const final { return !m_originClean; }
   bool isOffscreenCanvas() const final { return true; }
@@ skipping 26 matching lines @@
 
   bool isPaintable() const;
 
   std::unique_ptr<OffscreenCanvasFrameDispatcher> m_frameDispatcher;
   // cc::SurfaceId is broken into three integer components as this can be used
   // in transfer of OffscreenCanvas across threads
   // If this object is not created via
   // HTMLCanvasElement.transferControlToOffscreen(),
   // then the following members would remain as initialized zero values.
   uint32_t m_clientId = 0;
+  uint32_t m_sinkId = 0;
   uint32_t m_localId = 0;
   uint64_t m_nonce = 0;
 };
 
 }  // namespace blink
 
 #endif  // OffscreenCanvas_h