Add asserts to ensure that we:

src/mips/code-stubs-mips.h

Index: src/mips/code-stubs-mips.h
===================================================================
--- src/mips/code-stubs-mips.h	(revision 9277)
+++ src/mips/code-stubs-mips.h	(working copy)
@@ -578,6 +578,8 @@
                                      Register r0,
                                      Register r1);
 
+  virtual bool SometimesSetsUpAFrame() { return false; }
+
  private:
   static const int kInlinedProbes = 4;
   static const int kTotalProbes = 20;
@@ -590,7 +592,7 @@
       StringDictionary::kHeaderSize +
       StringDictionary::kElementsStartIndex * kPointerSize;
 
-  Major MajorKey() { return StringDictionaryNegativeLookup; }
+  Major MajorKey() { return StringDictionaryLookup; }
 
   int MinorKey() {
     return LookupModeBits::encode(mode_);