Cleanup scanner character streams.

- GenericStringUtf16CharacterStream::start_position_ was unused.
- GenericStringUtf16CharacterStream inherits from BufferedUtf16CharacterStream,
so no need to initialize buffer_cursor_ and buffer_end_ twice (this makes it
clearer which class in the inheritance chain takes care of which variables).

R=yangguo@chromium.org
BUG=

Review URL: https://codereview.chromium.org/216523004

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20334 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/scanner-character-streams.cc

@@ -126,8 +126,6 @@ GenericStringUtf16CharacterStream::GenericStringUtf16CharacterStream(
     : string_(data),
       length_(end_position) {
   ASSERT(end_position >= start_position);
-  buffer_cursor_ = buffer_;
-  buffer_end_ = buffer_;
   pos_ = start_position;
 }
 

src/scanner-character-streams.h

@@ -72,7 +72,6 @@ class GenericStringUtf16CharacterStream: public BufferedUtf16CharacterStream {
   virtual unsigned FillBuffer(unsigned position, unsigned length);
 
   Handle<String> string_;
-  unsigned start_position_;
   unsigned length_;
 };