Migrate from MathUtil::inverse() to gfx::Transform::GetInverse()

cc/layer_impl.cc

Index: cc/layer_impl.cc
diff --git a/cc/layer_impl.cc b/cc/layer_impl.cc
index e1cf9d49fd8695871fa11f6bc3ce5511864c715a..59ad8d8d83c43eaf9c09f749cc4e2de867709a5f 100644
--- a/cc/layer_impl.cc
+++ b/cc/layer_impl.cc
@@ -236,7 +236,9 @@ InputHandlerClient::ScrollStatus LayerImpl::tryScroll(const gfx::PointF& screenS
 
     if (!nonFastScrollableRegion().IsEmpty()) {
         bool clipped = false;
-        gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(MathUtil::inverse(screenSpaceTransform()), screenSpacePoint, clipped);
+        gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
+        screenSpaceTransform().GetInverse(&inverseScreenSpaceTransform);

[danakj, 2012/12/19 05:23:06]

If GetInverse() returns false, seems like we shouldn't use it? Should we pretend
the region is empty in that case, and cause impl scrolling when it might not
expect? Or pretend the region is infinite and scroll on the main thread when we
might have been ok to impl scroll? I guess the latter is safer?

+        gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(inverseScreenSpaceTransform, screenSpacePoint, clipped);
         gfx::PointF hitTestPointInLayerSpace = gfx::ScalePoint(hitTestPointInContentSpace, 1 / contentsScaleX(), 1 / contentsScaleY());
         if (!clipped && nonFastScrollableRegion().Contains(gfx::ToRoundedPoint(hitTestPointInLayerSpace))) {
             TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed nonFastScrollableRegion");