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diff --git a/Source/JavaScriptCore/wtf/MainThread.cpp b/Source/JavaScriptCore/wtf/MainThread.cpp
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+/*
+ * Copyright (C) 2007, 2008 Apple 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.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "MainThread.h"
+
+#include "CurrentTime.h"
+#include "Deque.h"
+#include "StdLibExtras.h"
+#include "Threading.h"
+
+#if PLATFORM(CHROMIUM)
+#error Chromium uses a different main thread implementation
+#endif
+
+namespace WTF {
+
+struct FunctionWithContext {
+    MainThreadFunction* function;
+    void* context;
+    ThreadCondition* syncFlag;
+
+    FunctionWithContext(MainThreadFunction* function = 0, void* context = 0, ThreadCondition* syncFlag = 0)
+        : function(function)
+        , context(context)
+        , syncFlag(syncFlag)
+    { 
+    }
+    bool operator == (const FunctionWithContext& o)
+    {
+        return function == o.function
+            && context == o.context
+            && syncFlag == o.syncFlag;
+    }
+};
+
+class FunctionWithContextFinder {
+public:
+    FunctionWithContextFinder(const FunctionWithContext& m) : m(m) {}
+    bool operator() (FunctionWithContext& o) { return o == m; }
+    FunctionWithContext m;
+};
+
+
+typedef Deque<FunctionWithContext> FunctionQueue;
+
+static bool callbacksPaused; // This global variable is only accessed from main thread.
+#if !PLATFORM(MAC) && !PLATFORM(QT)
+static ThreadIdentifier mainThreadIdentifier;
+#endif
+
+static Mutex& mainThreadFunctionQueueMutex()
+{
+    DEFINE_STATIC_LOCAL(Mutex, staticMutex, ());
+    return staticMutex;
+}
+
+static FunctionQueue& functionQueue()
+{
+    DEFINE_STATIC_LOCAL(FunctionQueue, staticFunctionQueue, ());
+    return staticFunctionQueue;
+}
+
+
+#if !PLATFORM(MAC)
+
+void initializeMainThread()
+{
+    static bool initializedMainThread;
+    if (initializedMainThread)
+        return;
+    initializedMainThread = true;
+
+#if !PLATFORM(QT)
+    mainThreadIdentifier = currentThread();
+#endif
+
+    mainThreadFunctionQueueMutex();
+    initializeMainThreadPlatform();
+}
+
+#else
+
+static pthread_once_t initializeMainThreadKeyOnce = PTHREAD_ONCE_INIT;
+
+static void initializeMainThreadOnce()
+{
+    mainThreadFunctionQueueMutex();
+    initializeMainThreadPlatform();
+}
+
+void initializeMainThread()
+{
+    pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadOnce);
+}
+
+static void initializeMainThreadToProcessMainThreadOnce()
+{
+    mainThreadFunctionQueueMutex();
+    initializeMainThreadToProcessMainThreadPlatform();
+}
+
+void initializeMainThreadToProcessMainThread()
+{
+    pthread_once(&initializeMainThreadKeyOnce, initializeMainThreadToProcessMainThreadOnce);
+}
+#endif
+
+// 0.1 sec delays in UI is approximate threshold when they become noticeable. Have a limit that's half of that.
+static const double maxRunLoopSuspensionTime = 0.05;
+
+void dispatchFunctionsFromMainThread()
+{
+    ASSERT(isMainThread());
+
+    if (callbacksPaused)
+        return;
+
+    double startTime = currentTime();
+
+    FunctionWithContext invocation;
+    while (true) {
+        {
+            MutexLocker locker(mainThreadFunctionQueueMutex());
+            if (!functionQueue().size())
+                break;
+            invocation = functionQueue().takeFirst();
+        }
+
+        invocation.function(invocation.context);
+        if (invocation.syncFlag)
+            invocation.syncFlag->signal();
+
+        // If we are running accumulated functions for too long so UI may become unresponsive, we need to
+        // yield so the user input can be processed. Otherwise user may not be able to even close the window.
+        // This code has effect only in case the scheduleDispatchFunctionsOnMainThread() is implemented in a way that
+        // allows input events to be processed before we are back here.
+        if (currentTime() - startTime > maxRunLoopSuspensionTime) {
+            scheduleDispatchFunctionsOnMainThread();
+            break;
+        }
+    }
+}
+
+void callOnMainThread(MainThreadFunction* function, void* context)
+{
+    ASSERT(function);
+    bool needToSchedule = false;
+    {
+        MutexLocker locker(mainThreadFunctionQueueMutex());
+        needToSchedule = functionQueue().size() == 0;
+        functionQueue().append(FunctionWithContext(function, context));
+    }
+    if (needToSchedule)
+        scheduleDispatchFunctionsOnMainThread();
+}
+
+void callOnMainThreadAndWait(MainThreadFunction* function, void* context)
+{
+    ASSERT(function);
+
+    if (isMainThread()) {
+        function(context);
+        return;
+    }
+
+    ThreadCondition syncFlag;
+    Mutex& functionQueueMutex = mainThreadFunctionQueueMutex();
+    MutexLocker locker(functionQueueMutex);
+    functionQueue().append(FunctionWithContext(function, context, &syncFlag));
+    if (functionQueue().size() == 1)
+        scheduleDispatchFunctionsOnMainThread();
+    syncFlag.wait(functionQueueMutex);
+}
+
+void cancelCallOnMainThread(MainThreadFunction* function, void* context)
+{
+    ASSERT(function);
+
+    MutexLocker locker(mainThreadFunctionQueueMutex());
+
+    FunctionWithContextFinder pred(FunctionWithContext(function, context));
+
+    while (true) {
+        // We must redefine 'i' each pass, because the itererator's operator= 
+        // requires 'this' to be valid, and remove() invalidates all iterators
+        FunctionQueue::iterator i(functionQueue().findIf(pred));
+        if (i == functionQueue().end())
+            break;
+        functionQueue().remove(i);
+    }
+}
+
+void setMainThreadCallbacksPaused(bool paused)
+{
+    ASSERT(isMainThread());
+
+    if (callbacksPaused == paused)
+        return;
+
+    callbacksPaused = paused;
+
+    if (!callbacksPaused)
+        scheduleDispatchFunctionsOnMainThread();
+}
+
+#if !PLATFORM(MAC) && !PLATFORM(QT) && !PLATFORM(BREWMP)
+bool isMainThread()
+{
+    return currentThread() == mainThreadIdentifier;
+}
+#endif
+
+} // namespace WTF