Add a scoping object to help block scripting during plugin destruction.

Source/core/loader/FrameLoader.cpp

Index: Source/core/loader/FrameLoader.cpp
diff --git a/Source/core/loader/FrameLoader.cpp b/Source/core/loader/FrameLoader.cpp
index 843337b4fc2f0eb35b0a8ebff7d8e26cdbc94b34..d4f3eb518fc0da607f7868956ddbf419445ddc19 100644
--- a/Source/core/loader/FrameLoader.cpp
+++ b/Source/core/loader/FrameLoader.cpp
@@ -80,6 +80,7 @@
 #include "core/svg/graphics/SVGImage.h"
 #include "core/xml/parser/XMLDocumentParser.h"
 #include "platform/Logging.h"
+#include "platform/ReentrantScriptForbiddenScope.h"
 #include "platform/UserGestureIndicator.h"
 #include "platform/network/HTTPParsers.h"
 #include "platform/network/ResourceRequest.h"
@@ -1002,6 +1003,7 @@ void FrameLoader::notifyIfInitialDocumentAccessed()
 void FrameLoader::commitProvisionalLoad()
 {
     ASSERT(client()->hasWebView());
+    ReentrantScriptForbiddenScope forbidPluginDestructorScripting;
     RefPtr<DocumentLoader> pdl = m_provisionalDocumentLoader;
     RefPtrWillBeRawPtr<LocalFrame> protect(m_frame.get());