New gn target video_frame_api.

This is in preparation for https://codereview.webrtc.org/2517173004/,
which needs some updates of downstream dependencies. This cl adds the
target to api/BUILD.gn, creates the directory api/video, and a single
harmless include file there.

BUG=webrtc:5880

Review-Url: https://codereview.webrtc.org/2546723003
Cr-Commit-Position: refs/heads/master@{#15385}

webrtc/api/BUILD.gn

@@ -368,6 +368,29 @@ rtc_source_set("transport_api") {
     "call/transport.h",
   ]
 }
+
+rtc_source_set("video_frame_api") {
+  sources = [
+    "video/video_rotation.h",
+  ]
+
+  deps = [
+    "../base:rtc_base_approved",
+  ]
+
+  # TODO(nisse): This logic is duplicated in multiple places.
+  # Define in a single place.
+  if (rtc_build_libyuv) {
+    deps += [ "$rtc_libyuv_dir" ]
+    public_deps = [
+      "$rtc_libyuv_dir",
+    ]
+  } else {
+    # Need to add a directory normally exported by libyuv.
+    include_dirs = [ "$rtc_libyuv_dir/include" ]
+  }
+}
+
 if (rtc_include_tests) {
   config("peerconnection_unittests_config") {
     # The warnings below are enabled by default. Since GN orders compiler flags

webrtc/api/video/video_rotation.h

@@ -0,0 +1,26 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_API_VIDEO_VIDEO_ROTATION_H_
+#define WEBRTC_API_VIDEO_VIDEO_ROTATION_H_
+
+namespace webrtc {
+
+// enum for clockwise rotation.
+enum VideoRotation {
+  kVideoRotation_0 = 0,
+  kVideoRotation_90 = 90,
+  kVideoRotation_180 = 180,
+  kVideoRotation_270 = 270
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_API_VIDEO_VIDEO_ROTATION_H_