[Cast] Size-Adaptable platform video encoders.

media/cast/sender/video_encoder.cc

Index: media/cast/sender/video_encoder.cc
diff --git a/media/cast/sender/video_encoder.cc b/media/cast/sender/video_encoder.cc
index d6b62a891cf6de13e5de9a6667f6470d7a80d441..d65bf3c8dc845dcf4ad0a8e808e474f7655060eb 100644
--- a/media/cast/sender/video_encoder.cc
+++ b/media/cast/sender/video_encoder.cc
@@ -3,11 +3,61 @@
 // found in the LICENSE file.
 
 #include "media/cast/sender/video_encoder.h"
-#include "media/cast/sender/video_frame_factory.h"
+
+#include "media/cast/sender/external_video_encoder.h"
+#include "media/cast/sender/video_encoder_impl.h"
+
+#if defined(OS_MACOSX)
+#include "media/cast/sender/h264_vt_encoder.h"
+#endif
 
 namespace media {
 namespace cast {
 
+// static
+scoped_ptr<VideoEncoder> VideoEncoder::Create(
+      const scoped_refptr<CastEnvironment>& cast_environment,
+      const VideoSenderConfig& video_config,
+      const StatusChangeCallback& status_change_cb,
+      const CreateVideoEncodeAcceleratorCallback& create_vea_cb,
+      const CreateVideoEncodeMemoryCallback& create_video_encode_memory_cb) {
+  // On MacOS or IOS, attempt to use the system VideoToolbox library to
+  // perform optimized H.264 encoding.
+#if defined(OS_MACOSX) || defined(OS_IOS)
+  if (!video_config.use_external_encoder &&
+      H264VideoToolboxEncoder::IsSupported(video_config)) {
+    return scoped_ptr<VideoEncoder>(
+        new SizeAdaptableH264VideoToolboxVideoEncoder(
+            cast_environment,
+            video_config,
+            status_change_cb));
+  }
+#endif  // defined(OS_MACOSX)
+
+  // If the system provides a hardware-accelerated encoder, use it.
+#if !defined(OS_IOS)
+  if (ExternalVideoEncoder::IsSupported(video_config)) {
+    return scoped_ptr<VideoEncoder>(new SizeAdaptableExternalVideoEncoder(
+        cast_environment,
+        video_config,
+        status_change_cb,
+        create_vea_cb,
+        create_video_encode_memory_cb));
+  }
+#endif  // !defined(OS_IOS)
+
+  // Attempt to use the software encoder implementation.
+  if (VideoEncoderImpl::IsSupported(video_config)) {
+    return scoped_ptr<VideoEncoder>(new VideoEncoderImpl(
+        cast_environment,
+        video_config,
+        status_change_cb));
+  }
+
+  // No encoder implementation will suffice.
+  return nullptr;
+}
+
 scoped_ptr<VideoFrameFactory> VideoEncoder::CreateVideoFrameFactory() {
   return nullptr;
 }