Google's Zineb Ait Bahajji announced on Google+ that they added a new filter to the Google Search Console report for apps named Search Appearance. This report will show you by keyword and other metrics who clicked the install button for your app.
Zineb said, "you can use that filter to see data about your 'install app' button in Google mobile search results." "Thanks to this, you can now see which queries your users typed to see the install button for your app, and also filter by country to see where most of your app users come from," she added.
Here is a screen shot of the report from my Google Search Console account for our app, you can click to enlarge:
Zineb explains "this feature doesn't show how many users actually completed the download process once in the play store."
With this, Google added an update to the chart, which is documented here:
Apps only: App install button data in search results added to the report. This change may increase the total number of clicks and impressions.
Forum discussion at Google+.