media: upgrade base::SharedMemory in video capture decoder

This replaces a legacy base::SharedMemory member with a
base::UnsafeSharedMemoryRegion and base::WritableMemoryMapping
pair. Functionality is unchanged, other than having separate
error messages for failure on region creation and region mapping.

Bug: 849207


Change-Id: I7f0123fddb02aa6f1cd093d1c142a780728822e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1697601Reviewed-by: Ricky Liang <jcliang@chromium.org>
Commit-Queue: Matthew Cary (CET) <mattcary@chromium.org>
Cr-Commit-Position: refs/heads/master@{#681749}

media/capture/video/chromeos/video_capture_jpeg_decoder_impl.cc

@@ -74,24 +74,33 @@ void VideoCaptureJpegDecoderImpl::DecodeCapturedData(
   }
 
   // Enlarge input buffer if necessary.
-  if (!in_shared_memory_.get() ||
-      in_buffer_size > in_shared_memory_->mapped_size()) {
+  if (!in_shared_region_.IsValid() || !in_shared_mapping_.IsValid() ||
+      in_buffer_size > in_shared_mapping_.size()) {
     // Reserve 2x space to avoid frequent reallocations for initial frames.
     const size_t reserved_size = 2 * in_buffer_size;
-    in_shared_memory_.reset(new base::SharedMemory);
-    if (!in_shared_memory_->CreateAndMapAnonymous(reserved_size)) {
+    in_shared_region_ = base::UnsafeSharedMemoryRegion::Create(reserved_size);
+    if (!in_shared_region_.IsValid()) {
       base::AutoLock lock(lock_);
       decoder_status_ = FAILED;
-      LOG(WARNING) << "CreateAndMapAnonymous failed, size=" << reserved_size;
+      LOG(WARNING) << "UnsafeSharedMemoryRegion::Create failed, size="
+                   << reserved_size;
+      return;
+    }
+    in_shared_mapping_ = in_shared_region_.Map();
+    if (!in_shared_mapping_.IsValid()) {
+      base::AutoLock lock(lock_);
+      decoder_status_ = FAILED;
+      LOG(WARNING) << "UnsafeSharedMemoryRegion::Map failed, size="
+                   << reserved_size;
       return;
     }
   }
-  memcpy(in_shared_memory_->memory(), data, in_buffer_size);
+  memcpy(in_shared_mapping_.memory(), data, in_buffer_size);
 
   // No need to lock for |in_buffer_id_| since IsDecoding_Locked() is false.
   in_buffer_id_ = next_bitstream_buffer_id_;
-  media::BitstreamBuffer in_buffer(in_buffer_id_, in_shared_memory_->handle(),
-                                   false /* read_only */, in_buffer_size);
+  media::BitstreamBuffer in_buffer(in_buffer_id_, in_shared_region_.Duplicate(),
+                                   in_buffer_size);
   // Mask against 30 bits, to avoid (undefined) wraparound on signed integer.
   next_bitstream_buffer_id_ = (next_bitstream_buffer_id_ + 1) & 0x3FFFFFFF;
 

media/capture/video/chromeos/video_capture_jpeg_decoder_impl.h

@@ -13,6 +13,7 @@
 
 #include "base/callback.h"
 #include "base/macros.h"
+#include "base/memory/unsafe_shared_memory_region.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequence_checker.h"
 #include "components/chromeos_camera/mojo_mjpeg_decode_accelerator.h"
@@ -26,7 +27,7 @@ namespace media {
 
 // Implementation of media::VideoCaptureJpegDecoder that delegates to a
 // chromeos_camera::mojom::MjpegDecodeAccelerator. When a frame is received in
-// DecodeCapturedData(), it is copied to |in_shared_memory| for IPC transport
+// DecodeCapturedData(), it is copied to |in_shared_region_| for IPC transport
 // to |decoder_|. When the decoder is finished with the frame, |decode_done_cb_|
 // is invoked. Until |decode_done_cb_| is invoked, subsequent calls to
 // DecodeCapturedData() are ignored.
@@ -100,7 +101,8 @@ class CAPTURE_EXPORT VideoCaptureJpegDecoderImpl
 
   // Shared memory to store JPEG stream buffer. The input BitstreamBuffer is
   // backed by this.
-  std::unique_ptr<base::SharedMemory> in_shared_memory_;
+  base::UnsafeSharedMemoryRegion in_shared_region_;
+  base::WritableSharedMemoryMapping in_shared_mapping_;
 
   STATUS decoder_status_;