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

third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp

Index: third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp
diff --git a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp
index 2007c5d81496f008d9a3228e482bb144f32c404f..0dc3080397913380145c904d25edbe6f0bf4029f 100644
--- a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp
+++ b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.cpp
@@ -91,11 +91,14 @@ void MediaControlDownloadButtonElement::SetIsWanted(bool wanted) {
   if (!IsWanted())
     return;
 
-  DCHECK(IsWanted());
   if (!show_use_counted_) {
     show_use_counted_ = true;
     RecordMetrics(DownloadActionMetrics::kShown);
   }
+
+  // If the button is wanted, show IPH if possible.
+  static_cast<MediaControlsImpl&>(GetMediaControls())
+      .MaybeDispatchDownloadIPHTrigger();
 }
 
 DEFINE_TRACE(MediaControlDownloadButtonElement) {