[oilpan] Remove ThreadAffinity::MainThreadOnly

Source/heap/ThreadState.cpp

Index: Source/heap/ThreadState.cpp
diff --git a/Source/heap/ThreadState.cpp b/Source/heap/ThreadState.cpp
index e05fad7848c8feb09597fd828a047727555060f7..87d319e89b7616e442ea75c41892788dc40b395b 100644
--- a/Source/heap/ThreadState.cpp
+++ b/Source/heap/ThreadState.cpp
@@ -171,6 +171,8 @@ private:
 };
 
 
+intptr_t* ThreadState::s_mainThreadStackBottom = 0;
+intptr_t* ThreadState::s_mainThreadStackTop = 0;
 WTF::ThreadSpecific<ThreadState*>* ThreadState::s_threadSpecific = 0;
 ThreadState ThreadState::s_mainThreadState;
 SafePointBarrier* ThreadState::s_safePointBarrier = 0;
@@ -192,6 +194,8 @@ void ThreadState::init(intptr_t* startOfStack)
     s_threadSpecific = new WTF::ThreadSpecific<ThreadState*>();
     s_safePointBarrier = new SafePointBarrier();
     s_mainThreadState.create(startOfStack);
+    s_mainThreadStackBottom = startOfStack;
+    s_mainThreadStackTop = reinterpret_cast<intptr_t*>(reinterpret_cast<Address>(startOfStack) - (1 << 16));
     attachedThreads().add(&s_mainThreadState);
 }