Don't declare GpuMemoryBuffer-based VideoFrame mappable

Bug: 982201, 997581
Change-Id: Ida6c3e961a5bd23d89a8c19d74d7ce05a96a3f1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1804195
Commit-Queue: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697080}

media/base/video_frame.cc

@@ -77,11 +77,14 @@ bool VideoFrame::IsStorageTypeMappable(VideoFrame::StorageType storage_type) {
       // level, DmaBufs are not mappable from userspace.
       storage_type != VideoFrame::STORAGE_DMABUFS &&
 #endif
+      // GpuMemoryBuffer is not mappable at VideoFrame level. In most places
+      // GpuMemoryBuffer is opaque to the CPU, and for places that really need
+      // to access the data on CPU they can get the buffer with
+      // GetGpuMemoryBuffer() and call gfx::GpuMemoryBuffer::Map().
       (storage_type == VideoFrame::STORAGE_UNOWNED_MEMORY ||
        storage_type == VideoFrame::STORAGE_OWNED_MEMORY ||
        storage_type == VideoFrame::STORAGE_SHMEM ||
-       storage_type == VideoFrame::STORAGE_MOJO_SHARED_BUFFER ||
-       storage_type == VideoFrame::STORAGE_GPU_MEMORY_BUFFER);
+       storage_type == VideoFrame::STORAGE_MOJO_SHARED_BUFFER);
 }
 
 // Checks if |source_format| can be wrapped into a |target_format| frame.