Remove uses of std::unary_function and std::binary_function.

ash/wm/overview/window_grid.cc

Index: ash/wm/overview/window_grid.cc
diff --git a/ash/wm/overview/window_grid.cc b/ash/wm/overview/window_grid.cc
index 2036d5549b3510750f283e390630c809f1fb26a9..e4157268fd43b8cc833d430616bd370b3ec71f3a 100644
--- a/ash/wm/overview/window_grid.cc
+++ b/ash/wm/overview/window_grid.cc
@@ -68,8 +68,7 @@ void CleanupWidgetAfterAnimationObserver::OnImplicitAnimationsCompleted() {
 }
 
 // A comparator for locating a given target window.
-struct WindowSelectorItemComparator
-    : public std::unary_function<WindowSelectorItem*, bool> {
+struct WindowSelectorItemComparator {
   explicit WindowSelectorItemComparator(const aura::Window* target_window)
       : target(target_window) {
   }