MIPS: Only dynamically perform access checks on the receiver if it's a JSGlobalProxy.

MIPS: Only dynamically perform access checks on the receiver if it's a JSGlobalProxy.

Port e9cdcb71743200e7dd18b0be62f764aa53729c63

Original commit message:
Proxies up the chain are guaranteed to provide access if we had access to the receiver, since otherwise we wouldn't have been able to compile the stub in the first place. If the security check would change, the window navigates, changing the map of the JSGlobalProxy.

BUG=

Review URL: https://codereview.chromium.org/958923002

Cr-Commit-Position: refs/heads/master@{#26894}