Add flexible keybinding/command system to sk_app

tools/viewer/Viewer.h

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef Viewer_DEFINED
 #define Viewer_DEFINED
 
 #include "sk_app/Application.h"
+#include "sk_app/CommandSet.h"
 #include "sk_app/Window.h"
 #include "gm.h"
 #include "SkAnimTimer.h"
 #include "Slide.h"
 
 class SkCanvas;
 
 class Viewer : public sk_app::Application {
 public:
     Viewer(int argc, char** argv, void* platformData);
     ~Viewer() override;
 
-    bool onKey(sk_app::Window::Key key, sk_app::Window::InputState state, uint32_t modifiers);
-    bool onChar(SkUnichar, uint32_t modifiers);
     void onPaint(SkCanvas* canvas);
     void onIdle(double ms) override;
 
 private:
     void initSlides();
     void updateTitle();
     void setupCurrentSlide(int previousSlide);
 
     void drawStats(SkCanvas* canvas);
 
@@ skipping 12 matching lines @@
 
     bool                   fDisplayStats;
 
     // transform data
     SkMatrix               fLocalMatrix;
     SkScalar               fZoomCenterX;
     SkScalar               fZoomCenterY;
     SkScalar               fZoomLevel;
     SkScalar               fZoomScale;
 
+    sk_app::CommandSet     fCommands;
 };
 
 
 #endif