DevTools: fix assertion failure when collecting async calls stacks

Source/core/inspector/InspectorDebuggerAgent.cpp

Index: Source/core/inspector/InspectorDebuggerAgent.cpp
diff --git a/Source/core/inspector/InspectorDebuggerAgent.cpp b/Source/core/inspector/InspectorDebuggerAgent.cpp
index a1017fe481fe1ae90fd8bb547fa6807dc3b52ce9..147f151e50ff55902fc38b897c19f91156d863b1 100644
--- a/Source/core/inspector/InspectorDebuggerAgent.cpp
+++ b/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;

[esprehn, 2015/08/19 22:43:53]

I think you want to use Optional<ScriptForbiddenScope::AllowUserAgentScript>
instead.

[yurys, 2015/08/20 00:05:09]

Didn't know that we have Optional, thanks! 
https://codereview.chromium.org/1286383007

+    if (isMainThread())
+        allowScripting = adoptPtr(new ScriptForbiddenScope::AllowUserAgentScript());
     return m_v8DebuggerAgent->currentAsyncStackTraceForConsole();
 }