Oilpan: handle thread-local weak tracing slightly better.

Source/platform/heap/StackFrameDepth.cpp

Index: Source/platform/heap/StackFrameDepth.cpp
diff --git a/Source/platform/heap/StackFrameDepth.cpp b/Source/platform/heap/StackFrameDepth.cpp
index caae8faaa1aa296f3037cb02eb8abfd9f2e2d5e5..ab2ae41693b510d84c2c8308ac3add89f699f358 100644
--- a/Source/platform/heap/StackFrameDepth.cpp
+++ b/Source/platform/heap/StackFrameDepth.cpp
@@ -20,6 +20,9 @@ namespace blink {
 static const char* s_avoidOptimization = nullptr;
 
 uintptr_t StackFrameDepth::s_stackFrameLimit = 0;
+#if ENABLE(ASSERT)
+bool StackFrameDepth::s_isActive = false;
+#endif
 
 // NEVER_INLINE ensures that |dummy| array on configureLimit() is not optimized away,
 // and the stack frame base register is adjusted |kSafeStackFrameSize|.
@@ -33,6 +36,10 @@ void StackFrameDepth::configureStackLimit()
 {
     static const int kStackRoomSize = 1024;
 
+#if ENABLE(ASSERT)
+    s_isActive = true;
+#endif
+
     size_t stackSize = getUnderestimatedStackSize();
     if (stackSize) {
         size_t stackBase = reinterpret_cast<size_t>(getStackStart());