Wires up MotionEvents for mojo_shell_apk on Android.

mojo/services/native_viewport/android/mojo_viewport.h

Index: mojo/services/native_viewport/android/mojo_viewport.h
diff --git a/mojo/services/native_viewport/android/mojo_viewport.h b/mojo/services/native_viewport/android/mojo_viewport.h
index 6c60285025ed398352f1f12507a0569363b19b8e..e26ff57448fc4e6a0958e8295d9203f462e2ce31 100644
--- a/mojo/services/native_viewport/android/mojo_viewport.h
+++ b/mojo/services/native_viewport/android/mojo_viewport.h
@@ -39,6 +39,9 @@ class MojoViewport {
   void SurfaceCreated(JNIEnv* env, jobject obj, jobject jsurface);
   void SurfaceDestroyed(JNIEnv* env, jobject obj);
   void SurfaceSetSize(JNIEnv* env, jobject obj, jint width, jint height);
+  bool MotionEvent(JNIEnv* env, jobject obj, jboolean is_touch,
+                   jint pointer_id, jint action, jfloat x, jfloat y,
+                   jlong time_ms);
 
  private:
   ~MojoViewport();