Add StringScanner.scanChar() and .expectChar().

Add StringScanner.scanChar() and .expectChar().

R=jmesserly@google.com

Committed: https://github.com/dart-lang/string_scanner/commit/f83ceb2e84a60a6417c6aeb0cd2162931617461a

[nweiz, 2016-06-06 23:23:03]

nweiz@google.com changed reviewers:
+ jmesserly@google.com

[Jennifer Messerly, 2016-06-06 23:46:51]

lgtm

https://codereview.chromium.org/2041813002/diff/1/lib/src/line_scanner.dart
File lib/src/line_scanner.dart (right):

https://codereview.chromium.org/2041813002/diff/1/lib/src/line_scanner.dart#n...
lib/src/line_scanner.dart:78: if (character == $lf || (character == $cr &&
peekChar() != $lf)) {
Would it be worth a doc comment on what the behavior is for newlines/returns?

I think the logic here makes sense though. Basically it will behave exactly like
readChar as far as updating the line info. So `scanChar(CR)` for example would
only update the line if there isn't an LF after it.

That said probably folks won't use this function to explicitly scanChar for LF
or CR. For that to be safe you'd want to do something like `scanChar(LF) ||
scanChar(CR) && (scanChar(LF) || true)` at which point you could use
scan(Pattern p) method below

[nweiz, 2016-06-06 23:51:34]

Code review changes

[nweiz, 2016-06-06 23:52:08]

Description was changed from

==========
Add StringScanner.scanChar() and .expectChar().
==========

to

==========
Add StringScanner.scanChar() and .expectChar().

R=jmesserly@google.com

Committed:
https://github.com/dart-lang/string_scanner/commit/f83ceb2e84a60a6417c6aeb0cd...
==========

[nweiz, 2016-06-06 23:52:09]

Committed patchset #2 (id:20001) manually as
f83ceb2e84a60a6417c6aeb0cd2162931617461a (presubmit successful).