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

cc/layer_tree_host.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_tree_host.h"
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
@@ skipping 778 matching lines @@
 gfx::PointF LayerTreeHost::adjustEventPointForPinchZoom(const gfx::PointF& zoomedViewportPoint)
     const
 {
     if (m_implTransform.IsIdentity())
         return zoomedViewportPoint;
 
     DCHECK(m_implTransform.IsInvertible());
 
     // Scale to screen space before applying implTransform inverse.
     gfx::PointF zoomedScreenspacePoint = gfx::ScalePoint(zoomedViewportPoint, deviceScaleFactor());
-    gfx::Transform inverseImplTransform = MathUtil::inverse(m_implTransform);
+
+    // Note carefully, this remains an identity matrix if m_implTransform is uninvertible.
+    // TODO: see if there is something more reasonable we can do if m_implTransform really is uninvertible.
+    //       or perhaps we can just DCHECK that m_implTransform should be invertible?
+    gfx::Transform inverseImplTransform(gfx::Transform::kSkipInitialization);
+    if (!m_implTransform.GetInverse(&inverseImplTransform))
+        inverseImplTransform.MakeIdentity();
 
     bool wasClipped = false;
     gfx::PointF unzoomedScreenspacePoint = MathUtil::projectPoint(inverseImplTransform, zoomedScreenspacePoint, wasClipped);
     DCHECK(!wasClipped);
 
     // Convert back to logical pixels for hit testing.
     gfx::PointF unzoomedViewportPoint = gfx::ScalePoint(unzoomedScreenspacePoint, 1 / deviceScaleFactor());
 
     return unzoomedViewportPoint;
 }
@@ skipping 84 matching lines @@
             else
                 layer->notifyAnimationFinished(wallClockTime.ToDoubleT());
         }
     }
 
     for (size_t childIndex = 0; childIndex < layer->children().size(); ++childIndex)
         setAnimationEventsRecursive(events, layer->children()[childIndex].get(), wallClockTime);
 }
 
 }  // namespace cc