chrome/blink: Add functionality for in-product help for media elements.

components/feature_engagement_tracker/public/feature_list.cc

 /// Copyright 2017 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.
 
 #include "components/feature_engagement_tracker/public/feature_list.h"
 
 #include "components/feature_engagement_tracker/public/feature_constants.h"
 
 namespace feature_engagement_tracker {
 
 namespace {
 // Whenever a feature is added to |kAllFeatures|, it should also be added as
 // DEFINE_VARIATION_PARAM below, and also added to the
 // |kIPHDemoModeChoiceVariations| array.
 const base::Feature* kAllFeatures[] = {
     &kIPHDummyFeature,  // Ensures non-empty array for all platforms.
 #if defined(OS_ANDROID)
     &kIPHDataSaverPreviewFeature,
     &kIPHDataSaverDetailFeature,
     &kIPHDownloadPageFeature,
     &kIPHDownloadHomeFeature,
+    &kIPHMediaDownloadFeature,
 #endif  // OS_ANDROID
 };
 }  // namespace
 
 const char kIPHDemoModeFeatureChoiceParam[] = "chosen_feature";
 
+const char kEnableMediaDownloadIPH[] = "enable_media_download_iph";
+
 std::vector<const base::Feature*> GetAllFeatures() {
   return std::vector<const base::Feature*>(
       kAllFeatures, kAllFeatures + arraysize(kAllFeatures));
 }
 
 }  // namespace feature_engagement_tracker