Add viewer mode to VisualBench.

tools/VisualBench/VisualModule.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
  */
 
 #ifndef VisualModule_DEFINED
 #define VisualModule_DEFINED
 
 #include "SkRefCnt.h"
 
 class SkCanvas;
 
 /*
  * VisualModule is the base class for all of the various types of activities VisualBench supports.
  *
  * The common theme tying these all together is they need to display an image to the screen.  Later,
  * on we some modules will also be interactive
  */
 class VisualModule : public SkRefCnt {
 public:
     virtual ~VisualModule() {}
 
     virtual void draw(SkCanvas* canvas)=0;
 
+    virtual bool onHandleChar(SkUnichar unichar) = 0;
+
 private:
     typedef SkRefCnt INHERITED;
 };
 
 #endif