[oilpan] Remove ThreadAffinity::MainThreadOnly

Source/heap/ThreadState.h

Index: Source/heap/ThreadState.h
diff --git a/Source/heap/ThreadState.h b/Source/heap/ThreadState.h
index 2f92dbd49c344d8cf8f1ceb07827083630681468..c5e5ac32d2737d6b48023c85d1a0346ac1005976 100644
--- a/Source/heap/ThreadState.h
+++ b/Source/heap/ThreadState.h
@@ -52,7 +52,7 @@ enum ThreadAffinity {
 // By default all types are considered to be used on the main thread only.
 template<typename T>
 struct ThreadingTrait {
-    static const ThreadAffinity Affinity = MainThreadOnly;
+    static const ThreadAffinity Affinity = AnyThread;
 };
 
 // Marks specified class as requiring thread safe handles which can be used from any thread.
@@ -225,7 +225,13 @@ public:
     static void attach(intptr_t* startOfStack);
     static void detach();
 
-    static ThreadState* Current() { return **s_threadSpecific; }
+    static ThreadState* Current()
+    {
+        // intptr_t dummy;
+        // if (LIKELY(s_mainThreadStackTop < &dummy && &dummy <= s_mainThreadStackBottom))
+        //    return MainThreadState();
+        return **s_threadSpecific;
+    }
     static ThreadState* MainThreadState() { return &s_mainThreadState; }
     static bool IsMainThread() { return Current() == MainThreadState(); }
 
@@ -274,6 +280,8 @@ public:
     Interruptor* interruptor() const { return m_interruptor; }
 
 private:
+    static intptr_t* s_mainThreadStackBottom;
+    static intptr_t* s_mainThreadStackTop;
     static WTF::ThreadSpecific<ThreadState*>* s_threadSpecific;
     static ThreadState s_mainThreadState;
     static SafePointBarrier* s_safePointBarrier;