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

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

Index: third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h
diff --git a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h
index dfc7f4b377057c9c82f19dc11189d7e2d6e2d2a3..dc30c5951ce875876573c7f7b2ca78b91a7bc16c 100644
--- a/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h
+++ b/third_party/WebKit/Source/modules/media_controls/elements/MediaControlDownloadButtonElement.h
@@ -5,6 +5,7 @@
 #ifndef MediaControlDownloadButtonElement_h
 #define MediaControlDownloadButtonElement_h
 
+#include "modules/ModulesExport.h"
 #include "modules/media_controls/elements/MediaControlInputElement.h"
 
 namespace blink {
@@ -12,7 +13,7 @@ namespace blink {
 class Event;
 class MediaControlsImpl;
 
-class MediaControlDownloadButtonElement final
+class MODULES_EXPORT MediaControlDownloadButtonElement final

[mlamouri (slow - plz ping), 2017/08/16 13:09:30]

Do you still need the export?

[Khushal, 2017/08/16 19:01:23]

The tests call SetIsWanted on the button to check that logic, so need the export
for that.

     : public MediaControlInputElement {
  public:
   explicit MediaControlDownloadButtonElement(MediaControlsImpl&);
@@ -30,6 +31,7 @@ class MediaControlDownloadButtonElement final
 
  protected:
   const char* GetNameForHistograms() const final;
+  void UpdateShownState() override;

[mlamouri (slow - plz ping), 2017/08/16 13:09:30]

Make it `final`?

[Khushal, 2017/08/16 19:01:23]

Done.

 
  private:
   // This is used for UMA histogram (Media.Controls.Download). New values should