Debug: support breakpoints set in the middle of statement (try #2 after rollback)

Review URL: https://codereview.chromium.org/18349004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15420 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Implement WeakMap.prototype.clear function.

R=rossberg@chromium.org
BUG=v8:2753
TEST=mjsunit/harmony/collections

Review URL: https://codereview.chromium.org/18352002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15421 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Derive synthetic type bounds for expressions

Currently synthesizes Smi as the lower bound for numeric operations (except for +, which might result in a string). That would need to change in places where we want to track constants as type feedback.

Does not do anything about variables yet.

R=jkummerow@chromium.org
BUG=

Review URL: https://codereview.chromium.org/17842004

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@15422 ce2b1a6d-e550-0410-aec6-3dcde31c8c00