X87: Encapsulate megamorphic load/tail-call in hydrogen

port r23772.

original commit message:

  To aid vector-based load ic work, we need to be able to handle
  the megamorphic load case in hydrogen. A simple approach is to
  wrap the probe activity in a hydrogen instruction.

  The instruction is novel in that it always tail-calls away.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/564683002

Patch from Jing Bao <jing.bao@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23889 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
X87: Initialize CodeStubInterfaceDescriptor in the constructor.

port r23773.

original commit message:

  Initialize CodeStubInterfaceDescriptor in the constructor.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/563133002

Patch from Jing Bao <jing.bao@intel.com>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@23890 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/master'