Add missing .h files to .gn files that have a .cc file next to it in the gn file already.

media/cast/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//third_party/protobuf/proto_library.gni")
 
@@ skipping 62 matching lines @@
   sources = [
     "net/cast_transport.h",
     "net/cast_transport_config.cc",
     "net/cast_transport_config.h",
     "net/cast_transport_defines.h",
     "net/cast_transport_impl.cc",
     "net/cast_transport_impl.h",
     "net/pacing/paced_sender.cc",
     "net/pacing/paced_sender.h",
     "net/rtcp/receiver_rtcp_event_subscriber.cc",
+    "net/rtcp/receiver_rtcp_event_subscriber.h",
     "net/rtcp/receiver_rtcp_session.cc",
     "net/rtcp/receiver_rtcp_session.h",
     "net/rtcp/rtcp_builder.cc",
     "net/rtcp/rtcp_builder.h",
     "net/rtcp/rtcp_defines.cc",
     "net/rtcp/rtcp_defines.h",
     "net/rtcp/rtcp_utility.cc",
     "net/rtcp/rtcp_utility.h",
     "net/rtcp/sender_rtcp_session.cc",
     "net/rtcp/sender_rtcp_session.h",
@@ skipping 210 matching lines @@
     "net/rtcp/test_rtcp_packet_builder.cc",
     "net/rtcp/test_rtcp_packet_builder.h",
     "net/rtp/cast_message_builder_unittest.cc",
     "net/rtp/frame_buffer_unittest.cc",
     "net/rtp/framer_unittest.cc",
     "net/rtp/mock_rtp_payload_feedback.cc",
     "net/rtp/mock_rtp_payload_feedback.h",
     "net/rtp/packet_storage_unittest.cc",
     "net/rtp/receiver_stats_unittest.cc",
     "net/rtp/rtp_packet_builder.cc",
+    "net/rtp/rtp_packet_builder.h",
     "net/rtp/rtp_packetizer_unittest.cc",
     "net/rtp/rtp_parser_unittest.cc",
     "net/udp_transport_unittest.cc",
     "receiver/audio_decoder_unittest.cc",
     "receiver/frame_receiver_unittest.cc",
     "receiver/video_decoder_unittest.cc",
     "sender/audio_encoder_unittest.cc",
     "sender/audio_sender_unittest.cc",
     "sender/congestion_control_unittest.cc",
     "sender/external_video_encoder_unittest.cc",
@@ skipping 217 matching lines @@
     ":sender",
   ]
 }
 
 static_library("cast_receiver") {
   complete_static_lib = true
   deps = [
     ":receiver",
   ]
 }