DevTools: fix assertion failure when collecting async calls stacks

BUG=522674

Review URL: https://codereview.chromium.org/1305433004

git-svn-id: svn://svn.chromium.org/blink/trunk@200854 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/inspector/InspectorDebuggerAgent.cpp

@@ -33,6 +33,8 @@
 #include "bindings/core/v8/V8Binding.h"
 #include "core/inspector/ScriptAsyncCallStack.h"
 #include "core/inspector/v8/V8Debugger.h"
+#include "platform/ScriptForbiddenScope.h"
+#include "wtf/MainThread.h"
 
 namespace blink {
 
@@ -259,6 +261,9 @@ bool InspectorDebuggerAgent::isPaused()
 
 PassRefPtrWillBeRawPtr<ScriptAsyncCallStack> InspectorDebuggerAgent::currentAsyncStackTraceForConsole()
 {
+    OwnPtr<ScriptForbiddenScope::AllowUserAgentScript> allowScripting;
+    if (isMainThread())
+        allowScripting = adoptPtr(new ScriptForbiddenScope::AllowUserAgentScript());
     return m_v8DebuggerAgent->currentAsyncStackTraceForConsole();
 }