Grab the address space lock before calling to Vmmap in mprotect
Grab the address space lock before calling to Vmmap in mprotect

Invoking NaClVmmapCheckExistingMapping without holding the
address space lock can lead to a potential race condition
since NaClVmmapCheckExistingMapping may reorder the Vmmap
entries.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3585
TESTS= small_tests
R=bsy@google.com

Review URL: https://codereview.chromium.org/19488003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@11833 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client,Lind-Project/native_client