Return MaybeHandle from NewConsString.

R=ishell@chromium.org

Review URL: https://codereview.chromium.org/223383002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20473 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Function calls are handled with a LoadIC and a FunctionCallStub. This works well, but we can create a platform to gather custom feedback by inventing a CallIC. CallIC takes a JSFunction as input, maintains UNINIT/MONO/MEGA state in a feedback slot, and engages in limited patching for the most efficient code.

The change creates a degrade in NBody tests, but a follow-on CL addresses it by using this custom feedback platform to give a 45% improvement.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/172523002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@20474 ce2b1a6d-e550-0410-aec6-3dcde31c8c00