Add support for inverse transform animations.

ui/compositor/transform_animation_curve_adapter.cc

Index: ui/compositor/transform_animation_curve_adapter.cc
diff --git a/ui/compositor/transform_animation_curve_adapter.cc b/ui/compositor/transform_animation_curve_adapter.cc
index 96500b3de521210c77a8bb853a5db7dace2e708c..3e6c049cf1d8e8cea4e8a170a32e96fd6213d2a6 100644
--- a/ui/compositor/transform_animation_curve_adapter.cc
+++ b/ui/compositor/transform_animation_curve_adapter.cc
@@ -51,4 +51,43 @@ gfx::Transform TransformAnimationCurveAdapter::GetValue(
   return gfx::ComposeTransform(to_return);
 }
 
+InverseTransformCurveAdapter::InverseTransformCurveAdapter(
+    TransformAnimationCurveAdapter base_curve,
+    gfx::Transform initial_value,
+    base::TimeDelta duration)
+    : base_curve_(base_curve),
+      initial_value_(initial_value),
+      duration_(duration) {
+  effective_initial_value_ = base_curve_.GetValue(0.0) * initial_value_;
+}
+
+InverseTransformCurveAdapter::~InverseTransformCurveAdapter() {
+}
+
+double InverseTransformCurveAdapter::Duration() const {
+  return duration_.InSeconds();
+}
+
+scoped_ptr<cc::AnimationCurve> InverseTransformCurveAdapter::Clone() const {
+  scoped_ptr<InverseTransformCurveAdapter> to_return(
+      new InverseTransformCurveAdapter(base_curve_,
+                                       initial_value_,
+                                       duration_));
+  return to_return.PassAs<cc::AnimationCurve>();
+}
+
+gfx::Transform InverseTransformCurveAdapter::GetValue(
+    double t) const {
+  if (t <= 0.0)
+    return initial_value_;
+
+  gfx::Transform base_transform = base_curve_.GetValue(t);
+  // Invert base
+  gfx::Transform to_return(gfx::Transform::kSkipInitialization);
+  DCHECK(base_transform.GetInverse(&to_return));
+
+  to_return.PreconcatTransform(effective_initial_value_);
+  return to_return;
+}
+
 }  // namespace ui