--- a/mobile/android/geckoview/src/main/java/org/mozilla/gecko/GeckoView.java
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/gecko/GeckoView.java
@@ -141,17 +141,16 @@ public class GeckoView extends LayerView
         @WrapForJNI(calledFrom = "gecko")
         private synchronized void onReattach(final GeckoView view) {
             if (view.mNativeQueue == mNativeQueue) {
                 return;
             }
             view.mNativeQueue.setState(mNativeQueue.getState());
             mNativeQueue = view.mNativeQueue;
         }
-
     }
 
     // Object to hold onto our nsWindow connection when GeckoView gets destroyed.
     private static class StateBinder extends Binder implements Parcelable {
         public final Parcelable superState;
         public final Window window;
 
         public StateBinder(Parcelable superState, Window window) {
@@ -1059,16 +1058,26 @@ public class GeckoView extends LayerView
     public interface ContentListener {
         /**
         * A page title was discovered in the content or updated after the content
         * loaded.
         * @param view The GeckoView that initiated the callback.
         * @param title The title sent from the content.
         */
         void onTitleChange(GeckoView view, String title);
+
+        /**
+         * A page has entered or exited full screen mode. Typically, the implementation
+         * would set the Activity containing the GeckoView to full screen when the page is
+         * in full screen mode.
+         *
+         * @param view The GeckoView that initiated the callback.
+         * @param fullScreen True if the page is in full screen mode.
+         */
+        void onFullScreen(GeckoView view, boolean fullScreen);
     }
 
     public interface NavigationListener {
         /**
         * A view has started loading content from the network.
         * @param view The GeckoView that initiated the callback.
         * @param url The resource being loaded.
         */