Use intptr_t for onTouch argument.

On 64-bit platforms, casting int to void* is not valid.
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2047443002

Review-Url: https://codereview.chromium.org/2047443002
diff --git a/tools/viewer/sk_app/Window.cpp b/tools/viewer/sk_app/Window.cpp
index 1c798df..7ec8baa 100644
--- a/tools/viewer/sk_app/Window.cpp
+++ b/tools/viewer/sk_app/Window.cpp
@@ -27,7 +27,7 @@
     return false;
 }
 
-static bool default_touch_func(int owner, Window::InputState state, float x, float y,
+static bool default_touch_func(intptr_t owner, Window::InputState state, float x, float y,
                                void* userData) {
     return false;
 }
@@ -62,7 +62,7 @@
     return fMouseFunc(x, y, state, modifiers, fMouseUserData);
 }
 
-bool Window::onTouch(int owner, InputState state, float x, float y) {
+bool Window::onTouch(intptr_t owner, InputState state, float x, float y) {
     return fTouchFunc(owner, state, x, y, fTouchUserData);
 }