Fixing assertion.

R=mstarzinger@chromium.org

Review URL: http://codereview.chromium.org/8218013

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9574 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/code-stubs-x64.cc

@@ -4084,7 +4084,7 @@ void StringCharCodeAtGenerator::GenerateFast(MacroAssembler* masm) {
                  Heap::kEmptyStringRootIndex);
   __ j(not_equal, &call_runtime_);
   // Get the first of the two strings and load its instance type.
-  ASSERT(kScratchRegister != scratch_);
+  ASSERT(!kScratchRegister.is(scratch_));
   __ movq(kScratchRegister, FieldOperand(object_, ConsString::kFirstOffset));
   __ jmp(&assure_seq_string, Label::kNear);