Support external buffer import in VDA interface and add a V4L2SVDA impl.

media/video/video_decode_accelerator.h

Index: media/video/video_decode_accelerator.h
diff --git a/media/video/video_decode_accelerator.h b/media/video/video_decode_accelerator.h
index 6722e2b97193157308fc43e68da692a01cc293bf..950f3c5e32715227fa9f4c491c6d375790d2a4ca 100644
--- a/media/video/video_decode_accelerator.h
+++ b/media/video/video_decode_accelerator.h
@@ -17,6 +17,7 @@
 #include "media/base/video_decoder_config.h"
 #include "media/video/picture.h"
 #include "ui/gfx/geometry/size.h"
+#include "ui/gfx/gpu_memory_buffer.h"
 
 typedef unsigned int GLenum;
 
@@ -102,6 +103,17 @@ class MEDIA_EXPORT VideoDecodeAccelerator {
   struct MEDIA_EXPORT Config {
     enum { kNoSurfaceID = SurfaceManager::kNoSurfaceID };
 
+    // Specifies the allocation and handling mode for output PictureBuffers.
+    // When set to ALLOCATE, the VDA is expected to allocate backing memory
+    // for PictureBuffers at the time of AssignPictureBuffers() call.
+    // When set to IMPORT, the VDA will not allocate, but after receiving
+    // AssignPictureBuffers() call, it will expect a call to
+    // ImportBufferForPicture() for each PictureBuffer before use.
+    enum class OutputMode {
+      ALLOCATE,
+      IMPORT,
+    };
+
     Config() = default;
     Config(VideoCodecProfile profile);
     Config(const VideoDecoderConfig& video_decoder_config);
@@ -125,6 +137,8 @@ class MEDIA_EXPORT VideoDecodeAccelerator {
 
     // Coded size of the video frame hint, subject to change.
     gfx::Size initial_expected_coded_size;
+
+    OutputMode output_mode = OutputMode::ALLOCATE;
   };
 
   // Interface for collaborating with picture interface to provide memory for
@@ -230,6 +244,19 @@ class MEDIA_EXPORT VideoDecodeAccelerator {
   virtual void AssignPictureBuffers(
       const std::vector<PictureBuffer>& buffers) = 0;
 
+  // Imports |gpu_memory_buffer_handles| as backing memory for picture buffer
+  // associated with |picture_buffer_id|. The n-th element in
+  // |gpu_memory_buffer_handles| should be a handle to a GpuMemoryBuffer backing
+  // the n-th plane of the PictureBuffer. This can only be be used if the VDA
+  // has been Initialize()d with config.output_mode = IMPORT, and should be
+  // preceded by a call to AssignPictureBuffers() to set up the number of
+  // PictureBuffers and their details.
+  // After this call, the VDA becomes the owner of the GpuMemoryBufferHandles,
+  // and is responsible for closing them after use, also on import failure.
+  virtual void ImportBufferForPicture(
+      int32_t picture_buffer_id,
+      const std::vector<gfx::GpuMemoryBufferHandle>& gpu_memory_buffer_handles);
+
   // Sends picture buffers to be reused by the decoder. This needs to be called
   // for each buffer that has been processed so that decoder may know onto which
   // picture buffers it can write the output to.
@@ -294,6 +321,10 @@ class MEDIA_EXPORT VideoDecodeAccelerator {
   // TODO(dshwang): after moving to D3D11, remove this. crbug.com/438691
   virtual GLenum GetSurfaceInternalFormat() const;
 
+  // In IMPORT OutputMode, if supported by the VDA, return the format that it
+  // requires for imported picture buffers.
+  virtual VideoPixelFormat GetOutputFormat() const;
+
  protected:
   // Do not delete directly; use Destroy() or own it with a scoped_ptr, which
   // will Destroy() it properly by default.