Add sample mouse support to Viewer

Bug: skia:6830
Change-Id: I1a6bb781465a29cec4946462e234d63c48693454
Reviewed-on: https://skia-review.googlesource.com/66543
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
diff --git a/tools/viewer/Slide.h b/tools/viewer/Slide.h
index 9ec7a3d..e23a2eb 100644
--- a/tools/viewer/Slide.h
+++ b/tools/viewer/Slide.h
@@ -11,6 +11,7 @@
 #include "SkRefCnt.h"
 #include "SkSize.h"
 #include "SkString.h"
+#include "sk_app/Window.h"
 
 class SkCanvas;
 class SkAnimTimer;
@@ -29,9 +30,12 @@
     virtual void unload() {}
 
     virtual bool onChar(SkUnichar c) { return false; }
+    virtual bool onMouse(SkScalar x, SkScalar y, sk_app::Window::InputState state,
+                         uint32_t modifiers) { return false; }
 
     SkString getName() { return fName; }
 
+
 protected:
     SkString    fName;
 };