Add drawer with state information

tools/viewer/sk_app/Window.cpp

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #include "Window.h"
 
 #include "SkSurface.h"
@@ skipping 14 matching lines @@
 static bool default_mouse_func(int x, int y, Window::InputState state, uint32_t modifiers, 
                                void* userData) {
     return false;
 }
 
 static bool default_touch_func(int owner, Window::InputState state, float x, float y,
                                void* userData) {
     return false;
 }
 
+static void default_ui_state_changed_func(
+        const SkString& stateName, const SkString& stateValue, void* userData) {}
+
 static void default_paint_func(SkCanvas*, void* userData) {}
 
 Window::Window() : fCharFunc(default_char_func)
                  , fKeyFunc(default_key_func)
                  , fMouseFunc(default_mouse_func)
                  , fTouchFunc(default_touch_func)
+                 , fUIStateChangedFunc(default_ui_state_changed_func)
                  , fPaintFunc(default_paint_func) {
 }
 
 void Window::detach() {
     delete fWindowContext;
     fWindowContext = nullptr;
 }
 
 bool Window::onChar(SkUnichar c, uint32_t modifiers) {
     return fCharFunc(c, modifiers, fCharUserData);
 }
 
 bool Window::onKey(Key key, InputState state, uint32_t modifiers) {
     return fKeyFunc(key, state, modifiers, fKeyUserData);
 }
 
 bool Window::onMouse(int x, int y, InputState state, uint32_t modifiers) {
     return fMouseFunc(x, y, state, modifiers, fMouseUserData);
 }
 
 bool Window::onTouch(int owner, InputState state, float x, float y) {
     return fTouchFunc(owner, state, x, y, fTouchUserData);
 }
 
+void Window::onUIStateChanged(const SkString& stateName, const SkString& stateValue) {
+    return fUIStateChangedFunc(stateName, stateValue, fUIStateChangedUserData);
+}
+
 void Window::onPaint() {
     markInvalProcessed();
     sk_sp<SkSurface> backbuffer = fWindowContext->getBackbufferSurface();
     if (backbuffer) {
         // draw into the canvas of this surface
         SkCanvas* canvas = backbuffer->getCanvas();
 
         fPaintFunc(canvas, fPaintUserData);
 
         canvas->flush();
@@ skipping 24 matching lines @@
         fIsContentInvalidated = true;
         onInval();
     }
 }
 
 void Window::markInvalProcessed() {
     fIsContentInvalidated = false;
 }
 
 }   // namespace sk_app