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..93ec812ab4f1d4bcdeb5c08247bfa294662162f7 100644
--- a/ui/compositor/transform_animation_curve_adapter.cc
+++ b/ui/compositor/transform_animation_curve_adapter.cc
@@ -51,4 +51,44 @@ gfx::Transform TransformAnimationCurveAdapter::GetValue(
   return gfx::ComposeTransform(to_return);
 }
 
+CounterTransformCurveAdapter::CounterTransformCurveAdapter(
+    TransformAnimationCurveAdapter parent_curve,
+    gfx::Transform initial_value,
+    base::TimeDelta duration)
+    : parent_curve_(parent_curve),
+      initial_value_(initial_value),
+      duration_(duration) {
+        effective_initial_value_ = parent_curve_.GetValue(0.0)
+                                   * initial_value_;

[Ian Vollick, 2013/08/23 12:45:19]

nit: weird leading whitespace.

[avallee, 2013/08/23 15:01:19]

Done.

+}
+
+CounterTransformCurveAdapter::~CounterTransformCurveAdapter() {
+}
+
+double CounterTransformCurveAdapter::Duration() const {
+  return duration_.InSeconds();
+}
+
+scoped_ptr<cc::AnimationCurve> CounterTransformCurveAdapter::Clone() const {
+  scoped_ptr<CounterTransformCurveAdapter> to_return(
+      new CounterTransformCurveAdapter(parent_curve_,
+                                       initial_value_,
+                                       duration_));
+  return to_return.PassAs<cc::AnimationCurve>();
+}
+
+gfx::Transform CounterTransformCurveAdapter::GetValue(
+    double t) const {
+  if (t <= 0.0)
+    return initial_value_;
+
+  gfx::Transform parent_transform = parent_curve_.GetValue(t);
+  // Invert parent
+  gfx::Transform to_return(gfx::Transform::kSkipInitialization);
+  DCHECK(parent_transform.GetInverse(&to_return));
+
+  to_return.PreconcatTransform(effective_initial_value_);
+  return to_return;
+}
+
 }  // namespace ui