Allow native_viewport to create new native windows on demand on Android.

services/native_viewport/platform_viewport_x11.cc

Index: services/native_viewport/platform_viewport_x11.cc
diff --git a/services/native_viewport/platform_viewport_x11.cc b/services/native_viewport/platform_viewport_x11.cc
index 951dba81e9d2170bcd44931d2d3d4bfa42dfe6bb..0fa851be27b33ace002c5b107ffc8f542bfb7547 100644
--- a/services/native_viewport/platform_viewport_x11.cc
+++ b/services/native_viewport/platform_viewport_x11.cc
@@ -34,8 +34,7 @@ float ConvertUIWheelValueToMojoValue(int offset) {
 class PlatformViewportX11 : public PlatformViewport,
                             public ui::PlatformWindowDelegate {
  public:
-  explicit PlatformViewportX11(Delegate* delegate) : delegate_(delegate) {
-  }
+  explicit PlatformViewportX11(Delegate* delegate) : delegate_(delegate) {}
 
   ~PlatformViewportX11() override {
     // Destroy the platform-window while |this| is still alive.
@@ -151,6 +150,11 @@ class PlatformViewportX11 : public PlatformViewport,
 
   void OnActivationChanged(bool active) override {}
 
+  bool NewNativeSurfaceAvailable() override {
+    NOTIMPLEMENTED() << "Native surface attaching not implemented.";
+    return false;
+  }
+
   scoped_ptr<ui::PlatformEventSource> event_source_;
   scoped_ptr<ui::PlatformWindow> platform_window_;
   Delegate* delegate_;