indicate an exception. All usages but one changed to return
MaybeHandles, and to use macros around the call.

The remaining work is in Compiler::GetUnoptimizedCode(), and when
that is turned into a MaybeHandle, then the macros dealing with
null handle returns can be eliminated.

R=yangguo@chromium.org

Review URL: https://codereview.chromium.org/247013002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20877 ce2b1a6d-e550-0410-aec6-3dcde31c8c00