Cache the current token in some functions in the parser

Cache the current token in some functions in the parser

Avoid some calls to CurrentToken(). Compiling all of dart2js, this saves
about 10% of calls to CurrentToken(). There is no measurable performance
difference (using wall-clock time).

R=iposva@google.com, srdjan@google.com

Committed: https://code.google.com/p/dart/source/detail?r=36763

[hausner, 2014-05-27 23:50:50]

Not sure whether Srdjan is able to look at this,  so adding Ivan as well.

This is a follow-up to Srdjan's change of splitting CurrentToken into a fast
path that gets inlined and a slow path.

[srdjan, 2014-05-28 02:25:13]

LGTM.

https://codereview.chromium.org/305653002/diff/1/runtime/vm/parser.cc
File runtime/vm/parser.cc (right):

https://codereview.chromium.org/305653002/diff/1/runtime/vm/parser.cc#newcode...
runtime/vm/parser.cc:10737: token == Token::kLBRACE) {
Add parentheses here and below.

[Ivan Posva, 2014-05-28 06:38:30]

LGTM -ip

[hausner, 2014-05-28 20:21:05]

Committed patchset #1 manually as r36763 (presubmit successful).