DevTools: speculative fix of crash in PageDebuggerAgent::restore

Source/core/inspector/PageDebuggerAgent.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 76 matching lines @@
 
 void PageDebuggerAgent::enable(ErrorString* errorString)
 {
     if (!canExecuteScripts()) {
         *errorString = "Script execution is prohibited";
         return;
     }
     InspectorDebuggerAgent::enable(errorString);
 }
 
+void PageDebuggerAgent::restore()
+{
+    if (canExecuteScripts())
+        InspectorDebuggerAgent::restore();
+}
+
 void PageDebuggerAgent::enable()
 {
     ASSERT(canExecuteScripts());
     InspectorDebuggerAgent::enable();
     m_instrumentingAgents->setPageDebuggerAgent(this);
 }
 
 void PageDebuggerAgent::disable()
 {
     InspectorDebuggerAgent::disable();
@@ skipping 111 matching lines @@
     RefPtrWillBeRawPtr<LocalFrame> protect(frame);
     InspectorDebuggerAgent::runScript(errorString, scriptId, executionContextId, objectGroup, doNotPauseOnExceptionsAndMuteConsole, result, exceptionDetails);
 
     if (frame)
         InspectorInstrumentation::didEvaluateScript(cookie);
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("devtools.timeline"), "UpdateCounters", TRACE_EVENT_SCOPE_THREAD, "data", InspectorUpdateCountersEvent::data());
 
 }
 
 } // namespace blink