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..7d3c42657296fd3d7deda29254f1d02fd7ad9dd0 100644
--- a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
+++ b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.h
@@ -59,10 +59,10 @@ class CORE_EXPORT OffscreenCanvas final
   const IntSize& Size() const override { return size_; }
   void SetSize(const IntSize&);
 
-  void SetPlaceholderCanvasId(int canvas_id) {
+  void SetPlaceholderCanvasId(uint64_t canvas_id) {
     placeholder_canvas_id_ = canvas_id;
   }
-  int PlaceholderCanvasId() const { return placeholder_canvas_id_; }
+  uint64_t PlaceholderCanvasId() const { return placeholder_canvas_id_; }
   bool HasPlaceholderCanvas() {
     return placeholder_canvas_id_ != kNoPlaceholderCanvas;
   }
@@ -167,10 +167,10 @@ 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;
+  uint64_t placeholder_canvas_id_ = kNoPlaceholderCanvas;
 
   IntSize size_;
   bool is_neutered_ = false;