Unify handling of position info in AST, part 1

Unify handling of position info in AST, part 1

* AstNode now has a position info.
* Removed various ad-hoc position infos from subclasses (most of which had it).
* Position is always set with the constructor, instead of later.
* Take care to use kNoPosition in the right spots, to not crash the debugger.

Still to do:

* Eliminate Conditional::then/else_position and WhileStatement::condition_position.
* Make CaseClause a proper AstNode and eliminate its custom position.
* If possible, eliminate all uses of kNoPosition.

R=yangguo@chromium.org
BUG=

Committed: http://code.google.com/p/v8/source/detail?r=17183

[Yang, 2013-09-24 16:04:15]

LGTM with comments.

https://codereview.chromium.org/24076007/diff/1/src/parser.cc
File src/parser.cc (right):

https://codereview.chromium.org/24076007/diff/1/src/parser.cc#newcode655
src/parser.cc:655: int beg_pos = scanner().location().beg_pos;
you could just use position() here, right?

https://codereview.chromium.org/24076007/diff/1/src/parser.cc#newcode3261
src/parser.cc:3261: position());  // TODO(rossberg): ???
What does this mean?

https://codereview.chromium.org/24076007/diff/1/src/parser.cc#newcode3297
src/parser.cc:3297: position());  // TODO(rossberg): ???
Ditto.

[rossberg, 2013-10-14 09:25:10]

Committed patchset #1 manually as r17183 (presubmit successful).