Constant-folding through HForceRepresentation fix.

Reverts changes in HValue::IsInteger32Constant() made in https://code.google.com/p/v8/source/detail?r=17787

R=bmeurer@chromium.org, mvstanton@chromium.org

Review URL: https://codereview.chromium.org/68493005

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17863 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Properly initialize desc->origin in the ARM assembler.

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/76073003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17865 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Make number of available threads isolate-dependent and expose it to ResourceConstraints.

R=svenpanne@chromium.org
BUG=v8:2991
LOG=Y

Review URL: https://codereview.chromium.org/68203029

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@17866 ce2b1a6d-e550-0410-aec6-3dcde31c8c00