Implement touch control

tools/viewer/sk_app/Window.h

Index: tools/viewer/sk_app/Window.h
diff --git a/tools/viewer/sk_app/Window.h b/tools/viewer/sk_app/Window.h
index f233f131a5eb15f1ce6bf5865502c3a339291197..39b06f2cd9ef0e2569d9f90420460b70f82dd76b 100644
--- a/tools/viewer/sk_app/Window.h
+++ b/tools/viewer/sk_app/Window.h
@@ -9,8 +9,9 @@
 #define Window_DEFINED
 
 #include "DisplayParams.h"
-#include "SkTypes.h"
 #include "SkRect.h"
+#include "SkTouchGesture.h"
+#include "SkTypes.h"
 
 class SkCanvas;
 
@@ -124,6 +125,7 @@ public:
     bool onChar(SkUnichar c, uint32_t modifiers);
     bool onKey(Key key, InputState state, uint32_t modifiers);
     bool onMouse(int x, int y, InputState state, uint32_t modifiers);
+    bool onTouch(int owner, InputState state, float x, float y);  // multi-owner = multi-touch
     void onPaint();
     void onResize(uint32_t width, uint32_t height);
 
@@ -133,6 +135,9 @@ public:
     virtual const DisplayParams& getDisplayParams();
     void setDisplayParams(const DisplayParams& params);
 
+    const SkMatrix& getGestureLocalM();
+    const SkMatrix& getGestureGlobalM() const;
+
 protected:
     Window();
 
@@ -148,7 +153,9 @@ protected:
     OnPaintFunc  fPaintFunc;
     void*        fPaintUserData;
 
-    WindowContext* fWindowContext;
+    WindowContext* fWindowContext = nullptr;
+
+    SkTouchGesture fGesture;
 };
 
 }   // namespace sk_app