DevTools: support TRACE_VALUE_TYPE_COPY_STRING

Source/core/inspector/TraceEventDispatcher.cpp

Index: Source/core/inspector/TraceEventDispatcher.cpp
diff --git a/Source/core/inspector/TraceEventDispatcher.cpp b/Source/core/inspector/TraceEventDispatcher.cpp
index c403e2489809b053dd801e8e6d43310e092e5047..c67163ec45cdc0f886489ea889e55d68e69bd1e2 100644
--- a/Source/core/inspector/TraceEventDispatcher.cpp
+++ b/Source/core/inspector/TraceEventDispatcher.cpp
@@ -151,11 +151,12 @@ const TraceEvent::TraceValueUnion& TraceEventDispatcher::TraceEvent::parameter(c
 {
     static WebCore::TraceEvent::TraceValueUnion missingValue;
     size_t index = findParameter(name);
+    ASSERT(isMainThread());
     if (index == kNotFound || m_argumentTypes[index] != expectedType) {
         ASSERT_NOT_REACHED();
         return missingValue;
     }
-    return *reinterpret_cast<const WebCore::TraceEvent::TraceValueUnion*>(m_argumentValues + index);
+    return m_argumentValues[index];
 }
 
 } // namespace WebCore