Parser / Scanner: Minor refactorings to make streaming scripts work easier.

Parser / Scanner: Minor refactorings to make streaming scripts work easier.

1) Call DeserializeScopeChain only if it's going to do something
non-trivial. And we only need to internalize the AstValueFactory in those cases.

2) BufferedUtf16CharacterStream::FillBuffer doesn't need the length
argument. The length is always kBufferSize and the subclasses can just read it
(it's protected).

R=rossberg@chromium.org
BUG=

Committed: https://code.google.com/p/v8/source/detail?r=22307

[marja, 2014-07-09 13:38:05]

rossberg, ptal

[rossberg, 2014-07-09 14:12:59]

lgtm

[marja, 2014-07-09 14:50:32]

Committed patchset #1 manually as r22307 (presubmit successful).