Introduce base::SharedMemory::TakeHandle() to take ownership of the handle
to shared memory. This is in order to avoid unnecessary DuplicateHandle(),
or GiveToProcess(), which is already taken care of by mojo, since these
shm handles go over a mojo message-pipe.

BUG=643746
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2496783002
Cr-Commit-Position: refs/heads/master@{#432022}