Remove some uses of MaybeObject methods.

test/cctest/test-strings.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1069 matching lines @@
   };
 
   const char* line;
   for (int i = 0; (line = lines[i]); i++) {
     printf("%s\n", line);
     v8::Local<v8::Value> result = v8::Script::Compile(
         v8::String::NewFromUtf8(CcTest::isolate(), line))->Run();
     CHECK_EQ(results[i]->IsUndefined(), result->IsUndefined());
     CHECK_EQ(results[i]->IsNumber(), result->IsNumber());
     if (result->IsNumber()) {
-      CHECK_EQ(Smi::cast(results[i]->ToSmi()->ToObjectChecked())->value(),
+      CHECK_EQ(Handle<Smi>::cast(Object::ToSmi(isolate, results[i]))->value(),
                result->ToInt32()->Value());
     }
   }
 }
 
 
 TEST(SliceFromCons) {
   FLAG_string_slices = true;
   CcTest::InitializeVM();
   Factory* factory = CcTest::i_isolate()->factory();
@@ skipping 314 matching lines @@
     dummy.Dispose();                                                           \
   }
 
 INVALID_STRING_TEST(NewStringFromAscii, char)
 INVALID_STRING_TEST(NewStringFromUtf8, char)
 INVALID_STRING_TEST(NewStringFromOneByte, uint8_t)
 INVALID_STRING_TEST(InternalizeOneByteString, uint8_t)
 INVALID_STRING_TEST(InternalizeUtf8String, char)
 
 #undef INVALID_STRING_TEST