Use a bezier timing function for the overview mode animation

ui/gfx/animation/tween.cc

Index: ui/gfx/animation/tween.cc
diff --git a/ui/gfx/animation/tween.cc b/ui/gfx/animation/tween.cc
index 174305078c27f8425e476d67bb0b5d70afe09351..6353902349b6e0920909ea3d95f970e058631066 100644
--- a/ui/gfx/animation/tween.cc
+++ b/ui/gfx/animation/tween.cc
@@ -14,6 +14,7 @@
 
 #include "base/basictypes.h"
 #include "base/logging.h"
+#include "ui/gfx/geometry/cubic_bezier.h"
 #include "ui/gfx/safe_integer_conversions.h"
 
 namespace gfx {
@@ -30,6 +31,9 @@ double Tween::CalculateValue(Tween::Type type, double state) {
     case EASE_IN_2:
       return pow(state, 4);
 
+    case EASE_IN_BEZIER:
+      return gfx::CubicBezier(.4, 0, 1, .2).Solve(state);
+
     case EASE_IN_OUT:
       if (state < 0.5)
         return pow(state * 2, 2) / 2.0;
@@ -48,6 +52,9 @@ double Tween::CalculateValue(Tween::Type type, double state) {
     case EASE_OUT:
       return 1.0 - pow(1.0 - state, 2);
 
+    case EASE_OUT_BEZIER:
+      return gfx::CubicBezier(.4, 0, .2, 1).Solve(state);
+
     case SMOOTH_IN_OUT:
       return sin(state);