Fix build failure on Win64 since r14458.

src/frames-inl.h

Index: src/frames-inl.h
diff --git a/src/frames-inl.h b/src/frames-inl.h
index 6ca1f1ff69868850549d3d026e6a6401375a2c36..7901a5e591c85f8d85431d7dbbecd426e64ab08d 100644
--- a/src/frames-inl.h
+++ b/src/frames-inl.h
@@ -236,7 +236,7 @@ inline int JavaScriptFrame::ComputeOperandsCount() const {
   ASSERT(IsAligned(stack_size_in_bytes, kPointerSize));
   ASSERT(type() == JAVA_SCRIPT);
   ASSERT(stack_size_in_bytes >= 0);
-  return stack_size_in_bytes >> kPointerSizeLog2;
+  return static_cast<int>(stack_size_in_bytes >> kPointerSizeLog2);
 }