Code: uint32_t ClientSharedBitmapManager::NotifyAllocatedSharedBitmap(
    base::SharedMemory* memory,
    const SharedBitmapId& id) {
  base::SharedMemoryHandle handle_to_send =
      base::SharedMemory::DuplicateHandle(memory->handle());
  if (!base::SharedMemory::IsHandleValid(handle_to_send)) {
    LOG(ERROR) << "Failed to duplicate shared memory handle for bitmap.";
    return 0;
   }
 
   mojo::ScopedSharedBufferHandle buffer_handle = mojo::WrapSharedMemoryHandle(
      handle_to_send, memory->mapped_size(), true /* read_only */);
 
   {
     base::AutoLock lock(lock_);
    (*shared_bitmap_allocation_notifier_)
        ->DidAllocateSharedBitmap(std::move(buffer_handle), id);
    return ++last_sequence_number_;
  }
}

Commit Message: Correct mojo::WrapSharedMemoryHandle usage

Fixes some incorrect uses of mojo::WrapSharedMemoryHandle which
were assuming that the call actually has any control over the memory
protection applied to a handle when mapped.

Where fixing usage is infeasible for this CL, TODOs are added to
annotate follow-up work.

Also updates the API and documentation to (hopefully) improve clarity
and avoid similar mistakes from being made in the future.

BUG=792900

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;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
Change-Id: I0578aaa9ca3bfcb01aaf2451315d1ede95458477
Reviewed-on: https://chromium-review.googlesource.com/818282
Reviewed-by: Wei Li <weili@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Yuzhu Shen <yzshen@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530268}
CWE ID: CWE-787
uint32_t ClientSharedBitmapManager::NotifyAllocatedSharedBitmap(
    base::SharedMemory* memory,
    const SharedBitmapId& id) {
  base::SharedMemoryHandle handle_to_send =
      base::SharedMemory::DuplicateHandle(memory->handle());
  if (!base::SharedMemory::IsHandleValid(handle_to_send)) {
    LOG(ERROR) << "Failed to duplicate shared memory handle for bitmap.";
    return 0;
   }
 
   mojo::ScopedSharedBufferHandle buffer_handle = mojo::WrapSharedMemoryHandle(
      handle_to_send, memory->mapped_size(),
      mojo::UnwrappedSharedMemoryHandleProtection::kReadWrite);
 
   {
     base::AutoLock lock(lock_);
    (*shared_bitmap_allocation_notifier_)
        ->DidAllocateSharedBitmap(std::move(buffer_handle), id);
    return ++last_sequence_number_;
  }
}
