Remove kInvalidStrictFlag and make gcc-4.5 happy again.

src/globals.h

Index: src/globals.h
diff --git a/src/globals.h b/src/globals.h
index 26a0e5f655fe6fe06fcea278f1418f4bc6bb0f1f..f85f286b38bf5dfbf0961dba271cc97fab98a6aa 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -364,11 +364,7 @@ template <typename T, class P = FreeStoreAllocationPolicy> class List;
 // The Strict Mode (ECMA-262 5th edition, 4.2.2).
 enum StrictModeFlag {
   kNonStrictMode,
-  kStrictMode,
-  // This value is never used, but is needed to prevent GCC 4.5 from failing
-  // to compile when we assert that a flag is either kNonStrictMode or
-  // kStrictMode.
-  kInvalidStrictFlag
+  kStrictMode
 };