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

cc/layer_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_impl.h"
 
 #include "base/debug/trace_event.h"
 #include "base/stringprintf.h"
 #include "base/values.h"
 #include "cc/animation_registrar.h"
@@ skipping 245 matching lines @@
         return InputHandlerClient::ScrollOnMainThread;
     }
 
     if (!screenSpaceTransform().IsInvertible()) {
         TRACE_EVENT0("cc", "LayerImpl::tryScroll: Ignored nonInvertibleTransform");
         return InputHandlerClient::ScrollIgnored;
     }
 
     if (!nonFastScrollableRegion().IsEmpty()) {
         bool clipped = false;
-        gfx::PointF hitTestPointInContentSpace = MathUtil::projectPoint(MathUtil::inverse(screenSpaceTransform()), screenSpacePoint, clipped);
+        // TODO: We shouldn't be applying a projection if screen space transform is uninvertible here.
+        //       Perhaps we should be returning ScrollOnMainThread if GetInverse returns false?
+        gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
+        if (!screenSpaceTransform().GetInverse(&inverseScreenSpaceTransform))
+            inverseScreenSpaceTransform.MakeIdentity();
+
+        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");
             return InputHandlerClient::ScrollOnMainThread;
         }
     }
 
     if (type == InputHandlerClient::Wheel && haveWheelEventHandlers()) {
         TRACE_EVENT0("cc", "LayerImpl::tryScroll: Failed wheelEventHandlers");
         return InputHandlerClient::ScrollOnMainThread;
@@ skipping 539 matching lines @@
 
 void LayerImpl::setVerticalScrollbarLayer(ScrollbarLayerImpl* scrollbarLayer)
 {
     if (!m_scrollbarAnimationController)
         m_scrollbarAnimationController = ScrollbarAnimationController::create(this);
     m_scrollbarAnimationController->setVerticalScrollbarLayer(scrollbarLayer);
     m_scrollbarAnimationController->updateScrollOffset(this);
 }
 
 }  // namespace cc