Make block writes in the serializer more efficient.

test/cctest/test-serialize.cc

 // Copyright 2007-2010 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 1036 matching lines @@
   Isolate* isolate = CcTest::i_isolate();
   isolate->compilation_cache()->Disable();  // Disable same-isolate code cache.
 
   Factory* f = isolate->factory();
 
   v8::HandleScope scope(CcTest::isolate());
 
   // Create a huge external internalized string to use as variable name.
   Vector<const uint8_t> string =
       ConstructSource(STATIC_CHAR_VECTOR(""), STATIC_CHAR_VECTOR("abcdef"),
-                      STATIC_CHAR_VECTOR(""), 1000000);
+                      STATIC_CHAR_VECTOR(""), 999999);

[vogelheim, 2014/10/23 16:48:44]

What's the significance of this change? Is this meant to trigger the padding
logic, since this string would now require padding?

[Yang, 2014/10/24 07:14:24]

yes.

   Handle<String> name = f->NewStringFromOneByte(string).ToHandleChecked();
   SerializerOneByteResource one_byte_resource(
       reinterpret_cast<const char*>(string.start()), string.length());
   name = f->InternalizeString(name);
   name->MakeExternal(&one_byte_resource);
   CHECK(name->IsExternalOneByteString());
   CHECK(name->IsInternalizedString());
   CHECK(isolate->heap()->InSpace(*name, LO_SPACE));
 
   // Create the source, which is "var <literal> = 42; <literal>".
@@ skipping 198 matching lines @@
     {
       DisallowCompilation no_compile(reinterpret_cast<Isolate*>(isolate2));
       script = v8::ScriptCompiler::CompileUnbound(
           isolate2, &source, v8::ScriptCompiler::kConsumeCodeCache);
     }
     v8::Local<v8::Value> result = script->BindToCurrentContext()->Run();
     CHECK(result->ToString()->Equals(v8_str("XY")));
   }
   isolate2->Dispose();
 }