cc: Fix comment about screenspace transform.

cc/layer_tree_host_common.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_common.h"
 
 #include "cc/layer.h"
 #include "cc/layer_impl.h"
 #include "cc/layer_iterator.h"
 #include "cc/layer_sorter.h"
@@ skipping 425 matching lines @@
     // The draw transform for the layer is:
     //        M[draw] = M[parent] * Tr[origin] * compositeLayerTransform * S[layer2content]
     //                = M[parent] * Tr[layer->position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
     //
     //        Interpreting the math left-to-right, this transforms from the layer's render surface to the origin of the layer in content space.
     //
     // The screen space transform is:
     //        M[screenspace] = M[root] * Tr[origin] * compositeLayerTransform * S[layer2content]
     //                       = M[root] * Tr[layer->position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
     //
-    //        Interpreting the math left-to-right, this transforms from the root render surface's content space to the local layer's origin in layer space.
+    //        Interpreting the math left-to-right, this transforms from the root render surface's content space to the origin of the layer in content space.
     //
     // The transform hierarchy that is passed on to children (i.e. the child's parentMatrix) is:
     //        M[parent]_for_child = M[parent] * Tr[origin] * compositeLayerTransform * compositeSublayerTransform
     //                            = M[parent] * Tr[layer->position() + anchor] * M[layer] * Tr[anchor2origin] * compositeSublayerTransform
     //
     //        and a similar matrix for the full hierarchy with respect to the root.
     //
     // Finally, note that the final matrix used by the shader for the layer is P * M[draw] * S . This final product
     // is computed in drawTexturedQuad(), where:
     //        P is the projection matrix
@@ skipping 469 matching lines @@
 
         foundLayer = currentLayer;
         break;
     }
 
     // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
     return foundLayer;
 }
 
 }  // namespace cc