Incorporates feedback by Nicolas for UTF-8 bytes based scanner CL

Incorporates feedback by Nicolas for UTF-8 bytes based scanner CL.

R=ngeoffray@google.com

Committed: https://code.google.com/p/dart/source/detail?r=29231

-----

https://chromiumcodereview.appspot.com/27510003/diff/28001/sdk/lib/_internal/compiler/implementation/scanner/scanner.dart#newcode166
/* Documentation in subclass [ArrayBasedScanner]. */
On 2013/10/18 10:19:37, ngeoffray wrote:
> So do the following methods only apply to the ArrayBasedScanner?

I just decided to put the documentation together with the actual implementation.
Technically the implementations could go here, but Peter preferred to separate
scanning code from token building code.

-----
https://chromiumcodereview.appspot.com/27510003/diff/28001/sdk/lib/_internal/compiler/implementation/scanner/utf8_bytes_scanner.dart#newcode140
throw "Invalid UTF-8 byte sequence: ${bytes.sublist(startOffset, end)}";
On 2013/10/18 10:19:37, ngeoffray wrote:
> Will users face this error? If yes, we should throw differently.

That could only happen in a file with wrong UTF-8 encoding, in which case
UTF8.decode would probably fail earlier. I could also just remove the check.

[ngeoffray, 2013-10-25 06:40:23]

LGTM!

[lukas, 2013-10-25 07:09:59]

Committed patchset #1 manually as r29231 (presubmit successful).