Moved transport.h from webrtc/ to webrtc/api, created build target and updated dependencies.

webrtc/modules/rtp_rtcp/BUILD.gn

 # Copyright (c) 2014 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("../../build/webrtc.gni")
 
@@ skipping 156 matching lines @@
     defines = [ "BWE_TEST_LOGGING_COMPILE_TIME_ENABLE=0" ]
   }
 
   if (!build_with_chromium && is_clang) {
     # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
     suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [
     "../..:webrtc_common",
+    "../../api:transport_api",
     "../../common_video",
     "../../system_wrappers",
     "../remote_bitrate_estimator",
   ]
 
   # TODO(jschuh): Bug 1348: fix this warning.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   if (is_win) {
     cflags = [
@@ skipping 12 matching lines @@
       "test/testFec/test_packet_masks_metrics.cc",
     ]
 
     deps = [
       ":rtp_rtcp",
       "//testing/gtest",
       "//webrtc/test:test_support_main",
     ]
   }  # test_packet_masks_metrics
 }