Android: enable H264&VP8 HW accelerator for MediaRecorder

media/ffmpeg/ffmpeg_common.cc

Index: media/ffmpeg/ffmpeg_common.cc
diff --git a/media/ffmpeg/ffmpeg_common.cc b/media/ffmpeg/ffmpeg_common.cc
index 950b9c0fd103672103d65048a7ad47ab48b89ee7..a241e0491bffc8f5b8ee35073dca92e858d55916 100644
--- a/media/ffmpeg/ffmpeg_common.cc
+++ b/media/ffmpeg/ffmpeg_common.cc
@@ -506,10 +506,13 @@ bool AVStreamToVideoDecoderConfig(const AVStream* stream,
       coded_size.set_height((coded_size.height() + 1) / 2 * 2);
   }
 
-  AVDictionaryEntry* webm_alpha =
-      av_dict_get(stream->metadata, "alpha_mode", nullptr, 0);
-  if (webm_alpha && !strcmp(webm_alpha->value, "1")) {
-    format = PIXEL_FORMAT_YV12A;
+  // H264 doesn't support alpha mode.
+  if (codec != kCodecH264) {
+    AVDictionaryEntry* webm_alpha =
+        av_dict_get(stream->metadata, "alpha_mode", nullptr, 0);
+    if (webm_alpha && !strcmp(webm_alpha->value, "1")) {
+      format = PIXEL_FORMAT_YV12A;
+    }
   }
 
   // Prefer the color space found by libavcodec if available.