Tidy up ConsoleMessage callstack inclusion, fix Worker console crashes

Source/core/workers/WorkerConsole.cpp

 /*
  * Copyright (C) 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2013 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 33 matching lines @@
     : m_scope(scope)
 {
 }
 
 WorkerConsole::~WorkerConsole()
 {
 }
 
 void WorkerConsole::reportMessageToConsole(PassRefPtrWillBeRawPtr<ConsoleMessage> consoleMessage)
 {
-    const ScriptCallFrame& lastCaller = consoleMessage->callStack()->at(0);
-    consoleMessage->setURL(lastCaller.sourceURL());
-    consoleMessage->setLineNumber(lastCaller.lineNumber());
+    if (RefPtrWillBeRawPtr<ScriptCallStack> callStack = consoleMessage->callStack()) {
+        const ScriptCallFrame& lastCaller = callStack->at(0);
+        consoleMessage->setURL(lastCaller.sourceURL());
+        consoleMessage->setLineNumber(lastCaller.lineNumber());
+    }

[kozyatinskiy1, 2014/09/15 12:57:25]

We have two places where we call this function: ConsoleBase::time/timeEnd and
internalAddMessage. If you add the collecting stack to time/timeEnd that I
missed then we do not need this check here. Because by default
createScriptCallStackForConsole and createScriptCallStackForConsole always
return at least one frame.

[sof, 2014/09/15 13:09:33]

That seems quite brittle - by inference, we should also remove it for the other
implementations of reportMessageToConsole() also? Which do not assume that a
callstack is present -- and should not afaict, as
createScriptCallStackForConsole() might return 0.

[kozyatinskiy1, 2014/09/15 13:31:29]

Ok, I agree with you but in this case, it is difficult to imagine a scenario in
which v8::Isolate would lose its context immediately after the console call and
createScriptCallStack* returns null.

     m_scope->addConsoleMessage(consoleMessage);
 }
 
 ExecutionContext* WorkerConsole::context()
 {
     if (!m_scope)
         return 0;
     return m_scope->executionContext();
 }
 
 void WorkerConsole::trace(Visitor* visitor)
 {
     visitor->trace(m_scope);
     ConsoleBase::trace(visitor);
 }
 
 // FIXME: add memory getter
 
 } // namespace blink