Add drawer with state information

tools/viewer/Viewer.h

Index: tools/viewer/Viewer.h
diff --git a/tools/viewer/Viewer.h b/tools/viewer/Viewer.h
index 0bafee175ba8b7d1165e3057dbb0495af2d075a4..2551ca977f81ff0130ecc59e68b4772621c93abe 100644
--- a/tools/viewer/Viewer.h
+++ b/tools/viewer/Viewer.h
@@ -8,12 +8,15 @@
 #ifndef Viewer_DEFINED
 #define Viewer_DEFINED
 
+#include <string>
+
 #include "sk_app/Application.h"
 #include "sk_app/CommandSet.h"
 #include "sk_app/Window.h"
 #include "gm.h"
 #include "SkAnimTimer.h"
 #include "Slide.h"
+#include "SkJSONCPP.h"
 
 class SkCanvas;
 
@@ -25,12 +28,15 @@ public:
     void onPaint(SkCanvas* canvas);
     void onIdle(double ms) override;
     bool onTouch(int owner, sk_app::Window::InputState state, float x, float y);
+    void onSet(const SkString& stateName, const SkString& stateValue);
 
 private:
     void initSlides();
     void updateTitle();
     void setupCurrentSlide(int previousSlide);
 
+    Json::Value getStateJson() const;
+
     void drawStats(SkCanvas* canvas);
 
     void changeZoomLevel(float delta);