Error: Manifest merger failed : uses-sdk:minSdkVersion 15 cannot be smaller than version 16 declared in library [com.google.android.gms:play-services-ads:19.2.0] C:\Users\HP.gradle\caches\transforms-2\files-2.1\e81645b3d583edffedf2649e74819131\jetified-play-services-ads-19.2.0\AndroidManifest.xml as the library might be using APIs not available in 15
This error did not come before downloading Ad view.
As the error message notes, this library does not work on API 15 (your minSdkVersion).
As API 14/15 support was dropped in version 19.0.0, you'll have to either update your minSdkVersion to at least 16 (the officially recommended approach), or use version 18.3.0 of any Play Services dependencies if you wish to continue supporting those devices. See this article for more detailed advice, as well as an additional alternative involving distributing multiple versions of your app.
