Allow apps to handle ad clicked/tapped events

Issue: #3106

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=163455563

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsLoader.java

@@ -61,7 +61,7 @@ public final class ImaAdsLoader implements Player.EventListener, VideoAdPlayer,
   /**
    * Listener for ad loader events. All methods are called on the main thread.
    */
-  public interface EventListener {
+  /* package */ interface EventListener {
 
     /**
      * Called when the ad playback state has been updated.
@@ -77,6 +77,16 @@ public final class ImaAdsLoader implements Player.EventListener, VideoAdPlayer,
      */
     void onLoadError(IOException error);
 
+    /**
+     * Called when the user clicks through an ad (for example, following a 'learn more' link).
+     */
+    void onAdClicked();
+
+    /**
+     * Called when the user taps a non-clickthrough part of an ad.
+     */
+    void onAdTapped();
+
   }
 
   static {
@@ -337,6 +347,16 @@ public final class ImaAdsLoader implements Player.EventListener, VideoAdPlayer,
         imaPausedContent = true;
         pauseContentInternal();
         break;
+      case TAPPED:
+        if (eventListener != null) {
+          eventListener.onAdTapped();
+        }
+        break;
+      case CLICKED:
+        if (eventListener != null) {
+          eventListener.onAdClicked();
+        }
+        break;
       case CONTENT_RESUME_REQUESTED:
         imaPausedContent = false;
         resumeContentInternal();

extensions/ima/src/main/java/com/google/android/exoplayer2/ext/ima/ImaAdsMediaSource.java

@@ -53,6 +53,16 @@ public final class ImaAdsMediaSource implements MediaSource {
      */
     void onAdLoadError(IOException error);
 
+    /**
+     * Called when the user clicks through an ad (for example, following a 'learn more' link).
+     */
+    void onAdClicked();
+
+    /**
+     * Called when the user taps a non-clickthrough part of an ad.
+     */
+    void onAdTapped();
+
   }
 
   private static final String TAG = "ImaAdsMediaSource";
@@ -305,6 +315,34 @@ public final class ImaAdsMediaSource implements MediaSource {
       });
     }
 
+    @Override
+    public void onAdClicked() {
+      if (eventHandler != null && eventListener != null) {
+        eventHandler.post(new Runnable() {
+          @Override
+          public void run() {
+            if (!released) {
+              eventListener.onAdClicked();
+            }
+          }
+        });
+      }
+    }
+
+    @Override
+    public void onAdTapped() {
+      if (eventHandler != null && eventListener != null) {
+        eventHandler.post(new Runnable() {
+          @Override
+          public void run() {
+            if (!released) {
+              eventListener.onAdTapped();
+            }
+          }
+        });
+      }
+    }
+
   }
 
 }