Fix ThreadHeap::isHeapObjectAlive(const T*& ptr) stack overflow.

third_party/WebKit/Source/platform/heap/HeapTest.cpp

Index: third_party/WebKit/Source/platform/heap/HeapTest.cpp
diff --git a/third_party/WebKit/Source/platform/heap/HeapTest.cpp b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
index c3d0aa58ecde03ca0c071339ef8076e59a984131..6a33c1cc563146fc36021d4193b32aa16d6e8f49 100644
--- a/third_party/WebKit/Source/platform/heap/HeapTest.cpp
+++ b/third_party/WebKit/Source/platform/heap/HeapTest.cpp
@@ -742,6 +742,11 @@ class ClassWithMember : public GarbageCollected<ClassWithMember> {
 
   DEFINE_INLINE_TRACE() {
     EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(this));
+
+    // Const pointer should also be alive. See http://crbug.com/661363.
+    const ClassWithMember* constPtr = static_cast<const ClassWithMember*>(this);
+    EXPECT_TRUE(ThreadHeap::isHeapObjectAlive(constPtr));
+
     if (!traceCount())
       EXPECT_FALSE(ThreadHeap::isHeapObjectAlive(m_traceCounter));
     else