Revert of Disallow users modify canvas after it transfers control to offscreen

third_party/WebKit/Source/core/html/HTMLCanvasElement.h

Index: third_party/WebKit/Source/core/html/HTMLCanvasElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLCanvasElement.h b/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
index d7fab2e7e84c881d6c20604a522b12cfab10edc2..027358b215260695c801c97b43e4983ac943b0d2 100644
--- a/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLCanvasElement.h
@@ -88,10 +88,19 @@
 
     const IntSize& size() const { return m_size; }
 
-    void setWidth(int, ExceptionState&);
-    void setHeight(int, ExceptionState&);
-
-    void setSize(const IntSize& newSize);
+    void setWidth(int);
+    void setHeight(int);
+
+    void setSize(const IntSize& newSize)
+    {
+        if (newSize == size())
+            return;
+        m_ignoreReset = true;
+        setWidth(newSize.width());
+        setHeight(newSize.height());
+        m_ignoreReset = false;
+        reset();
+    }
 
     // Called by Document::getCSSCanvasContext as well as above getContext().
     CanvasRenderingContext* getCanvasRenderingContext(const String&, const CanvasContextCreationAttributes&);