The talk bubble that will be introduced next to the article title will be a new entry point for article talk pages.
Flow:

What to measure:

• Measure clicks on the bubble in MobileWikiAppTalk as "action" = "bubble_click" and "source" will be "article_bubble"
• Add another new source as "article_side_panel" and log it as source when Talk page is opened from bubble->side panel -> talk page and "action" as always will be "open_talk"

@SNowick_WMF As we discussed, this will equip us to measure the number of users who clicked the bubble, and of them, how many actually opened the full view talk page? Please confirm.