Bug 1197957 - Introduce GeckoView.Window class; r=snorp

GeckoView.Window is a class that acts as the interface between
GeckoView in Java and nsWindow in C++. It will contain native methods
that GeckoView will use to interact with nsWindow.

On initialization, Window.open is called to create a nsWindow and
establish the JNI association between Window and the native nsWindow.
Then, whenever Window instance methods are called, the JNI stubs will
automatically call members of nsWindow.

mobile/android/base/GeckoView.java

@@ -12,8 +12,10 @@ import java.util.Set;
 
 import org.json.JSONException;
 import org.json.JSONObject;
+import org.mozilla.gecko.annotation.WrapForJNI;
 import org.mozilla.gecko.gfx.LayerView;
 import org.mozilla.gecko.mozglue.GeckoLoader;
+import org.mozilla.gecko.mozglue.JNIObject;
 import org.mozilla.gecko.util.Clipboard;
 import org.mozilla.gecko.util.EventCallback;
 import org.mozilla.gecko.util.GeckoEventListener;
@@ -104,6 +106,14 @@ public class GeckoView extends LayerView
         }
     };
 
+    @WrapForJNI
+    private static final class Window extends JNIObject {
+        static native void open(Window instance, int width, int height);
+        @Override protected native void disposeNative();
+    }
+
+    private final Window window = new Window();
+
     public GeckoView(Context context) {
         super(context);
         init(context, null, true);