Fix shortcutting bug in HInferRepresentation

Fix shortcutting bug in HInferRepresentation

* src/hydrogen.cc (HInferRepresentation::Analyze): Fix iterative loop
  over phis; the shortcutting behavior of || appears to be accidental
  here, causing O(n^2) convergence.  Not that it matters much, but hey!

While I'm at it, a minor comment fix:

* src/hydrogen-instructions.h (EnsureAndPropagateNotMinusZero): Fix a
  comment about the kinds of instructions that propagate to multiple
  inputs.

BUG=
TEST=passes tools/test.py

Review URL: http://codereview.chromium.org/7350019
Patch from Andy Wingo <wingo@igalia.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8645 ce2b1a6d-e550-0410-aec6-3dcde31c8c00