VideoToolbox encoder for cast senders.

media/cast/BUILD.gn

Index: media/cast/BUILD.gn
diff --git a/media/cast/BUILD.gn b/media/cast/BUILD.gn
index dde0a0bc3fd03d65c515182c37c4d08414cee46d..bffb4e625b3ac7caf762b09549aafc13b297a0a4 100644
--- a/media/cast/BUILD.gn
+++ b/media/cast/BUILD.gn
@@ -156,6 +156,14 @@ source_set("sender") {
       "sender/vp8_encoder.h",
     ]
   }
+
+  # iOS and OS X encoders
+  if (is_ios || is_mac) {
+    sources += [
+      "sender/h264_vt_encoder.cc",
+      "sender/h264_vt_encoder.h",
+    ]
+  }
 }
 
 source_set("receiver") {
@@ -304,6 +312,23 @@ test("cast_unittests") {
   ]
 }
 
+if (is_ios || is_mac) {
+  test("cast_h264_vt_encoder_unittests") {
+    sources = [
+      "sender/h264_vt_encoder_unittest.cc",
+    ]
+    deps = [
+      ":common",
+      ":sender",
+      ":test_support",
+      "//base/test:test_support",
+      "//testing/gmock",
+      "//testing/gtest",
+      "//third_party/ffmpeg",
+    ]
+  }
+}
+
 executable("generate_barcode_video") {
   testonly = true
   sources = [