Fix some stub calling asserts on x64.

src/mips/code-stubs-mips.cc

Index: src/mips/code-stubs-mips.cc
===================================================================
--- src/mips/code-stubs-mips.cc	(revision 9304)
+++ src/mips/code-stubs-mips.cc	(working copy)
@@ -3480,6 +3480,15 @@
 }
 
 
+bool CEntryStub::CompilingCallsToThisStubIsGCSafe() {
+  return !save_doubles_ && result_size_ == 1;
+}
+
+
+void CodeStub::GenerateStubsAheadOfTime() {
+}
+
+
 void CEntryStub::GenerateThrowTOS(MacroAssembler* masm) {
   __ Throw(v0);
 }