Prevent spinning up a layer tree view after closing

Source/web/WebViewImpl.cpp

Index: Source/web/WebViewImpl.cpp
diff --git a/Source/web/WebViewImpl.cpp b/Source/web/WebViewImpl.cpp
index a79c698484072414f1953b3cd1c6778c9d08d245..b36babbc47442d6a4d7e72058fd991f8edd02107 100644
--- a/Source/web/WebViewImpl.cpp
+++ b/Source/web/WebViewImpl.cpp
@@ -386,6 +386,7 @@ WebViewImpl::WebViewImpl(WebViewClient* client)
     , m_graphicsLayerFactory(adoptPtr(new GraphicsLayerFactoryChromium(this)))
     , m_isAcceleratedCompositingActive(false)
     , m_layerTreeViewCommitsDeferred(false)
+    , m_layerTreeViewClosed(false)
     , m_matchesHeuristicsForGpuRasterization(false)
     , m_recreatingGraphicsContext(false)
     , m_flingModifier(0)
@@ -2434,6 +2435,7 @@ void WebViewImpl::willCloseLayerTreeView()
 {
     setIsAcceleratedCompositingActive(false);
     m_layerTreeView = 0;
+    m_layerTreeViewClosed = true;
 }
 
 void WebViewImpl::didAcquirePointerLock()
@@ -3907,6 +3909,10 @@ void WebViewImpl::setIsAcceleratedCompositingActive(bool active)
     if (!m_client)
         return;
 
+    // In the middle of shutting down; don't try to spin back up a compositor.
+    if (m_layerTreeViewClosed)
+        return;
+
     if (!active) {
         m_isAcceleratedCompositingActive = false;
         if (!m_layerTreeViewCommitsDeferred