X87: CheckPrototypes uses weak cells to embed maps.

port 062a032f50291ce181462226ff41b4ef9b11deba

original commit message:

  CheckPrototypes uses weak cells to embed maps.

BUG=

Review URL: https://codereview.chromium.org/761093004

Cr-Commit-Position: refs/heads/master@{#25648}
X87: Use weak cells to embed maps in store handler.

port 3fc9c9b665baaa434c672efcbff632a2eae86f56

original commit message:

  Use weak cells to embed maps in store handler.
  BUG=v8:3629
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/779843002

Cr-Commit-Position: refs/heads/master@{#25649}