Build WTF as dll in component build

Source/wtf/MainThread.h

Index: Source/wtf/MainThread.h
diff --git a/Source/wtf/MainThread.h b/Source/wtf/MainThread.h
index 4649e33f82c04c6abea02426f2f74fffed6deb08..f9db1e2e662f96489cd7d19c952ef333c2c4c70e 100644
--- a/Source/wtf/MainThread.h
+++ b/Source/wtf/MainThread.h
@@ -32,20 +32,22 @@
 
 #include <stdint.h>
 
+#include "wtf/WTFExport.h"
+
 namespace WTF {
 
 typedef uint32_t ThreadIdentifier;
 typedef void MainThreadFunction(void*);
 
 // Must be called from the main thread.
-void initializeMainThread();
+WTF_EXPORT void initializeMainThread(void (*)(MainThreadFunction, void*));
 
-void callOnMainThread(MainThreadFunction*, void* context);
+WTF_EXPORT void callOnMainThread(MainThreadFunction*, void* context);
 
 template<typename> class Function;
-void callOnMainThread(const Function<void ()>&);
+WTF_EXPORT void callOnMainThread(const Function<void ()>&);
     
-bool isMainThread();
+WTF_EXPORT bool isMainThread();
 
 } // namespace WTF