cc: Add test for AA quads due to precision loss

cc/trees/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/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
@@ skipping 1391 matching lines @@
       globals.device_scale_factor,
       data_from_ancestor.in_subtree_of_page_scale_application_layer ?
           globals.page_scale_factor : 1.f,
       animating_transform_to_screen);
 
   // The draw_transform that gets computed below is effectively the layer's
   // draw_transform, unless the layer itself creates a render_surface. In that
   // case, the render_surface re-parents the transforms.
   layer_draw_properties.target_space_transform = combined_transform;
   // M[draw] = M[parent] * LT * S[layer2content]
-  layer_draw_properties.target_space_transform.Scale
-      (1.f / layer->contents_scale_x(), 1.f / layer->contents_scale_y());
+  SkMScalar one(1.0);

[danakj, 2013/09/07 00:54:59]

nit: use SK_MScalar1? or maybe not?

[enne (OOO), 2013/09/07 01:25:18]

Sure, done.

+  layer_draw_properties.target_space_transform.Scale(
+      one / layer->contents_scale_x(), one / layer->contents_scale_y());
 
   // The layer's screen_space_transform represents the transform between root
   // layer's "screen space" and local content space.
   layer_draw_properties.screen_space_transform =
       data_from_ancestor.full_hierarchy_matrix;
   if (!layer->preserves_3d())
     layer_draw_properties.screen_space_transform.FlattenTo2d();
   layer_draw_properties.screen_space_transform.PreconcatTransform
       (layer_draw_properties.target_space_transform);
 
@@ skipping 791 matching lines @@
   // At this point, we think the point does hit the touch event handler region
   // on the layer, but we need to walk up the parents to ensure that the layer
   // was not clipped in such a way that the hit point actually should not hit
   // the layer.
   if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl))
     return false;
 
   return true;
 }
 }  // namespace cc