Synchronize OffscreenCanvas content with the placeholder canvas

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

Index: third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
diff --git a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
index dd349c5992f4626c9653f1820fb09b272c0ed875..0d17fb305b42f419735807a7e87dfa803b1d853f 100644
--- a/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
+++ b/third_party/WebKit/Source/core/offscreencanvas/OffscreenCanvas.cpp
@@ -32,7 +32,7 @@ OffscreenCanvas* OffscreenCanvas::create(unsigned width, unsigned height) {
 void OffscreenCanvas::setWidth(unsigned width, ExceptionState& exceptionState) {
   // If this OffscreenCanvas is transferred control by an html canvas,
   // its size is determined by html canvas's size and cannot be resized.
-  if (m_canvasId >= 0) {
+  if (hasPlaceholderCanvas()) {
     exceptionState.throwDOMException(InvalidStateError,
                                      "Resizing is not allowed on an "
                                      "OffscreenCanvas that has been "
@@ -45,7 +45,7 @@ void OffscreenCanvas::setWidth(unsigned width, ExceptionState& exceptionState) {
 void OffscreenCanvas::setHeight(unsigned height,
                                 ExceptionState& exceptionState) {
   // Same comment as above.
-  if (m_canvasId >= 0) {
+  if (hasPlaceholderCanvas()) {
     exceptionState.throwDOMException(InvalidStateError,
                                      "Resizing is not allowed on an "
                                      "OffscreenCanvas that has been "
@@ -184,7 +184,8 @@ OffscreenCanvasFrameDispatcher* OffscreenCanvas::getOrCreateFrameDispatcher() {
     // (either main or worker) to the browser process and remains unchanged
     // throughout the lifetime of this OffscreenCanvas.
     m_frameDispatcher = wrapUnique(new OffscreenCanvasFrameDispatcherImpl(
-        m_clientId, m_sinkId, m_localId, m_nonce, width(), height()));
+        m_clientId, m_sinkId, m_localId, m_nonce, m_placeholderCanvasId,
+        width(), height()));
   }
   return m_frameDispatcher.get();
 }