Handlify the stub cache lookup and patching for CallIC and KeyedCallIC.

src/ic.h

Index: src/ic.h
diff --git a/src/ic.h b/src/ic.h
index ba33e1d7f5673f5ab189d74a6484c48e82a06793..9b305d93cd8a7b07c776434f42306b612c31058d 100644
--- a/src/ic.h
+++ b/src/ic.h
@@ -216,12 +216,12 @@ class CallICBase: public IC {
                              Handle<Object> object,
                              Code::ExtraICState* extra_ic_state);
 
-  MUST_USE_RESULT MaybeObject* ComputeMonomorphicStub(
-      LookupResult* lookup,
-      State state,
-      Code::ExtraICState extra_ic_state,
-      Handle<Object> object,
-      Handle<String> name);
+  // Compute a monomorphic stub if possible, otherwise return a null handle.
+  Handle<Code> ComputeMonomorphicStub(LookupResult* lookup,
+                                      State state,
+                                      Code::ExtraICState extra_state,
+                                      Handle<Object> object,
+                                      Handle<String> name);
 
   // Update the inline cache and the global stub cache based on the lookup
   // result.