Make preparser detect duplicate parameters and object literal properties.

Make preparser detect duplicate parameters and object literal properties.

This is a fix and reapply of r8516 with some comments addressed and more
tests added.
The difference from r8516 is that canonicalization of number literals is 
no performed using the same methods as in v8, to avoid false positives/negatives
when detecting duplicates.

Committed: http://code.google.com/p/v8/source/detail?r=8541

[Rico, 2011-07-06 07:55:11]

LGTM, please fix python indention to two characters + nit

http://codereview.chromium.org/7193045/diff/1016/src/preparser.cc
File src/preparser.cc (right):

http://codereview.chromium.org/7193045/diff/1016/src/preparser.cc#newcode1538
src/preparser.cc:1538: // Quick check for already being in canonical form.
Please assert that we actually have a number here, otherwise we could add, e.g.,
0.0 if we get an empty key

http://codereview.chromium.org/7193045/diff/1016/test/preparser/duplicate-par...
File test/preparser/duplicate-parameter.pyt (right):

http://codereview.chromium.org/7193045/diff/1016/test/preparser/duplicate-par...
test/preparser/duplicate-parameter.pyt:43: non_selfstrict, expectation)
The indention above makes this a bit hard to read, at least indent the last line
four more

http://codereview.chromium.org/7193045/diff/1016/test/preparser/duplicate-par...
test/preparser/duplicate-parameter.pyt:54: """, "id": "selfstrictnestedclean"}
Indention seems of for the 3 lines above

[Lasse Reichstein, 2011-07-06 08:20:00]

http://codereview.chromium.org/7193045/diff/1016/src/preparser.cc
File src/preparser.cc (right):

http://codereview.chromium.org/7193045/diff/1016/src/preparser.cc#newcode1538
src/preparser.cc:1538: // Quick check for already being in canonical form.
I'll assert the string isn't empty.
IsNumberCanonical doesn't accept an empty string, nor an invalid number literal,
but StringToDouble might accepts the empty string.
As for testing that it's a number, the number-parsing should do that fine.

http://codereview.chromium.org/7193045/diff/1016/test/preparser/duplicate-par...
File test/preparser/duplicate-parameter.pyt (right):

http://codereview.chromium.org/7193045/diff/1016/test/preparser/duplicate-par...
test/preparser/duplicate-parameter.pyt:54: """, "id": "selfstrictnestedclean"}
Those lines are part of a multiline string literal.