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

components/feature_engagement_tracker/public/feature_list.h

Index: components/feature_engagement_tracker/public/feature_list.h
diff --git a/components/feature_engagement_tracker/public/feature_list.h b/components/feature_engagement_tracker/public/feature_list.h
index b944137de77a9bfcd958c888b01c14dd4e2c43bc..c75d885effc263412fe69534f7ac6dd1a085d0ec 100644
--- a/components/feature_engagement_tracker/public/feature_list.h
+++ b/components/feature_engagement_tracker/public/feature_list.h
@@ -21,6 +21,10 @@ using FeatureVector = std::vector<const base::Feature*>;
 // feature (if any) was selected by the end user.
 extern const char kIPHDemoModeFeatureChoiceParam[];
 
+// The command-line flag used to enable media download IPH feature in the
+// renderer.
+extern const char kEnableMediaDownloadIPH[];
+
 namespace {
 
 // Defines a const flags_ui::FeatureEntry::FeatureParam for the given
@@ -49,6 +53,7 @@ DEFINE_VARIATION_PARAM(kIPHDataSaverPreviewFeature, "IPH_DataSaverPreview");
 DEFINE_VARIATION_PARAM(kIPHDataSaverDetailFeature, "IPH_DataSaverDetail");
 DEFINE_VARIATION_PARAM(kIPHDownloadPageFeature, "IPH_DownloadPage");
 DEFINE_VARIATION_PARAM(kIPHDownloadHomeFeature, "IPH_DownloadHome");
+DEFINE_VARIATION_PARAM(kIPHMediaDownloadFeature, "IPH_MediaDownload");
 #endif  // OS_ANDROID
 
 }  // namespace
@@ -63,6 +68,7 @@ constexpr flags_ui::FeatureEntry::FeatureVariation
         VARIATION_ENTRY(kIPHDataSaverDetailFeature),
         VARIATION_ENTRY(kIPHDownloadPageFeature),
         VARIATION_ENTRY(kIPHDownloadHomeFeature),
+        VARIATION_ENTRY(kIPHMediaDownloadFeature),
 #else
         VARIATION_ENTRY(kIPHDummyFeature),  // Ensures non-empty array.
 #endif  // OS_ANDROID