Move video_encoder.h and video_decoder.h to /api and create GN targets for them

webrtc/api/BUILD.gn

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("../webrtc.gni")
 if (is_android) {
@@ skipping 16 matching lines @@
     # TODO(kjellander): Add remaining dependencies when webrtc:4243 is done.
     ":audio_mixer_api",
     ":transport_api",
     "..:webrtc_common",
     "../base:rtc_base_approved",
     "../modules/audio_coding:audio_encoder_interface",
     "audio_codecs:audio_codecs_api",
   ]
 }
 
+rtc_source_set("video_decoder_api") {
+  sources = [
+    "video_decoder.h",
+  ]
+
+  deps = [
+    "..:webrtc_common",
+  ]
+}
+
+rtc_source_set("video_encoder_api") {
+  sources = [
+    "video_encoder.h",
+  ]
+
+  deps = [
+    "..:webrtc_common",
+    "../base:rtc_base_approved",
+
+    # TODO(ilnik): Add dependency on webrtc/video_frame.h when it will have it's
+    # own build target.
+  ]
+}
+
 rtc_static_library("libjingle_peerconnection_api") {
   check_includes = false  # TODO(kjellander): Remove (bugs.webrtc.org/6828)
   cflags = []
   sources = [
     "datachannel.h",
     "datachannelinterface.h",
     "dtmfsenderinterface.h",
     "jsep.h",
     "jsepicecandidate.h",
     "jsepsessiondescription.h",
@@ skipping 194 matching lines @@
       suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
     }
 
     deps = [
       ":libjingle_peerconnection_api",
       ":ortc_api",
       "//webrtc/test:test_support",
     ]
   }
 }