Avoid depending on ffmpeg by default (#131)

Author: taste1981

modules/video_coding/BUILD.gn

@@ -504,16 +504,22 @@ rtc_library("webrtc_h264") {
   visibility = [ "*" ]
   sources = [
     "codecs/h264/h264.cc",
-    "codecs/h264/h264_color_space.cc",
-    "codecs/h264/h264_color_space.h",
-    "codecs/h264/h264_decoder_impl.cc",
-    "codecs/h264/h264_decoder_impl.h",
     "codecs/h264/h264_encoder_impl.cc",
     "codecs/h264/h264_encoder_impl.h",
     "codecs/h264/include/h264.h",
   ]
 
   defines = []
+  if (ffmpeg_branding == "Chrome" || ffmpeg_branding == "Chromium") {
+    sources += [
+      "codecs/h264/h264_color_space.cc",
+      "codecs/h264/h264_color_space.h",
+      "codecs/h264/h264_decoder_impl.cc",
+      "codecs/h264/h264_decoder_impl.h",
+    ]
+    defines += [ "OWT_USE_FFMPEG" ]
+  }
+
   deps = [
     ":video_codec_interface",
     ":video_coding_utility",
@@ -543,10 +549,12 @@ rtc_library("webrtc_h264") {
   ]
 
   if (rtc_use_h264) {
-    deps += [
-      "//third_party/ffmpeg",
-      "//third_party/openh264:encoder",
-    ]
+    deps += [ "//third_party/openh264:encoder" ]
+
+    if (ffmpeg_branding == "Chrome" || ffmpeg_branding == "Chromium") {
+      deps += [ "//third_party/ffmpeg" ]
+    }
+
     if (!build_with_mozilla) {
       deps += [ "../../media:rtc_media_base" ]
     }

modules/video_coding/codecs/h264/h264.cc

@@ -21,7 +21,9 @@
 #include "rtc_base/trace_event.h"
 
 #if defined(WEBRTC_USE_H264)
+#if defined (OWT_USE_FFMPEG)
 #include "modules/video_coding/codecs/h264/h264_decoder_impl.h"
+#endif
 #include "modules/video_coding/codecs/h264/h264_encoder_impl.h"
 #endif
 
@@ -152,11 +154,16 @@ std::unique_ptr<H264Decoder> H264Decoder::Create() {
 #if defined(WEBRTC_USE_H264)
   RTC_CHECK(g_rtc_use_h264);
   RTC_LOG(LS_INFO) << "Creating H264DecoderImpl.";
+#if defined(OWT_USE_FFMPEG)
   return std::make_unique<H264DecoderImpl>();
 #else
   RTC_DCHECK_NOTREACHED();
   return nullptr;
 #endif
+#else
+  RTC_NOTREACHED();
+  return nullptr;
+#endif
 }
 
 bool H264Decoder::IsSupported() {