libdmabufheap: add mutex header file am: 02f3328777 am: f58c4d8dc3 am: 6f0294cd2e

Original change: https://android-review.googlesource.com/c/platform/system/memory/libdmabufheap/+/2219228

Change-Id: Id20e436b77d0b46137e4bc9af7122ffd28c9b57d
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
tree: 0e78bc199fb94d45f7713be92d256e16dde9e049
  1. include/
  2. tests/
  3. Android.bp
  4. BufferAllocator.cpp
  5. BufferAllocatorWrapper.cpp
  6. OWNERS
  7. PREUPLOAD.cfg