[Oilpan] Set stack limit using estimated sizes

Source/platform/heap/ThreadState.cpp

Index: Source/platform/heap/ThreadState.cpp
diff --git a/Source/platform/heap/ThreadState.cpp b/Source/platform/heap/ThreadState.cpp
index fb3061f56e3381ea5b25ba375bc969e1aa2da6e7..230801275137e5a862d5e2eac9e0a07f05a0ff62 100644
--- a/Source/platform/heap/ThreadState.cpp
+++ b/Source/platform/heap/ThreadState.cpp
@@ -254,7 +254,9 @@ ThreadState::ThreadState()
 
     if (isMainThread()) {
         s_mainThreadStackStart = reinterpret_cast<uintptr_t>(m_startOfStack) - sizeof(void*);
-        s_mainThreadUnderestimatedStackSize = StackFrameDepth::getUnderestimatedStackSize() - sizeof(void*);
+        size_t underestimatedStackSize = StackFrameDepth::getUnderestimatedStackSize();
+        if (underestimatedStackSize > 0)
+            s_mainThreadUnderestimatedStackSize = underestimatedStackSize - sizeof(void*);
     }
 
     for (int heapIndex = 0; heapIndex < LargeObjectHeapIndex; heapIndex++)