Adding third_party/openh264 build files for encoding

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index f58231fc4d16d6b9cdbed524e920c349566a2ae1..fedf8fdd38bc3f06d82890a40242572eecaac9dc 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -13,6 +13,7 @@ import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//build_overrides/v8.gni")
 import("//media/media_options.gni")
+import("//third_party/openh264/openh264_args.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
@@ -92,6 +93,7 @@ group("both_gn_and_gyp") {
     "//skia:skia_unittests",
     "//sql:sql_unittests",
     "//sync:sync_unit_tests",
+    "//third_party/openh264/testing:openh264_unittests",

[Dirk Pranke, 2015/11/21 00:48:51]

Are you sure you want to add this unconditionally, rather than just if
use_openh264 is true?

In the non-use_openh264 case, it'll be an empty binary, admittedly, but that
still adds a bit of overhead.

It's fine either way, just double-checking.

[hbos_chromium, 2015/11/23 09:06:13]

If we can make trybots conditionally run the binary then we don't need to
produce it unconditionally. For now I'll produce a binary either way to avoid
the risk of trybots running an old binary that shouldn't run.

     "//ui/base:ui_base_unittests",
     "//ui/gfx:gfx_unittests",
     "//url:url_unittests",
@@ -586,6 +588,15 @@ group("both_gn_and_gyp") {
   if (is_chromecast) {
     deps += [ "//chromecast:cast_shell" ]
   }
+
+  if (use_openh264) {
+    deps += [
+      "//third_party/openh264:openh264_common",
+      "//third_party/openh264:openh264_processing",
+      "//third_party/openh264:openh264_encoder",
+      "//third_party/openh264:openh264_decoder",
+    ]
+  }
 }
 
 group("gn_only") {