Change cc::ElementId to be a uint64_t

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

Index: third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
diff --git a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
index 3d5b7820d210832b2a1f854bdb9c52183ed40784..b92b735f817e98bdbcfa0d06008804d25fbbb2f8 100644
--- a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
+++ b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
@@ -7,6 +7,7 @@
 
 #include <memory>
 #include "bindings/core/v8/ScriptPromise.h"
+#include "core/dom/DOMNodeIds.h"
 #include "core/events/EventTarget.h"
 #include "core/html/HTMLCanvasElement.h"
 #include "core/html/canvas/CanvasImageSource.h"
@@ -59,10 +60,10 @@ class CORE_EXPORT OffscreenCanvas final
   const IntSize& Size() const override { return size_; }
   void SetSize(const IntSize&);
 
-  void SetPlaceholderCanvasId(int canvas_id) {
+  void SetPlaceholderCanvasId(DOMNodeId canvas_id) {
     placeholder_canvas_id_ = canvas_id;
   }
-  int PlaceholderCanvasId() const { return placeholder_canvas_id_; }
+  DOMNodeId PlaceholderCanvasId() const { return placeholder_canvas_id_; }
   bool HasPlaceholderCanvas() {
     return placeholder_canvas_id_ != kNoPlaceholderCanvas;
   }
@@ -167,10 +168,10 @@ class CORE_EXPORT OffscreenCanvas final
   WeakMember<ExecutionContext> execution_context_;
 
   enum {
-    kNoPlaceholderCanvas = -1,  // DOMNodeIds starts from 0, using -1 to
-                                // indicate no associated canvas element.
+    kNoPlaceholderCanvas = 0,  // DOMNodeIds starts from 1, using 0 to
+                               // indicate no associated canvas element.
   };
-  int placeholder_canvas_id_ = kNoPlaceholderCanvas;
+  DOMNodeId placeholder_canvas_id_ = kNoPlaceholderCanvas;
 
   IntSize size_;
   bool is_neutered_ = false;