X87: Remove code object from StackHandler.
X87: Remove code object from StackHandler.

port e0aa8ebf933b4c659e1c4a01ba244c5de452ff1c (r27103).

original commit message:

  This reduces the size of the StackHandler by one word. We no longer
  need to keep track of the code object, as the stack walk finds it.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/1022403002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#27353}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh