cc: Don't DCHECK for layers with non-invertible transforms.

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 44 matching lines @@
   gfx::Rect minimal_surface_rect = target_surface_rect;
   minimal_surface_rect.Intersect(layer_rect_in_target_space);
 
   // Project the corners of the target surface rect into the layer space.
   // This bounding rectangle may be larger than it needs to be (being
   // axis-aligned), but is a reasonable filter on the space to consider.
   // Non-invertible transforms will create an empty rect here.
 
   gfx::Transform surface_to_layer(gfx::Transform::kSkipInitialization);
   if (!transform.GetInverse(&surface_to_layer)) {
-    // TODO(shawnsingh): Either we need to handle uninvertible transforms
-    // here, or DCHECK that the transform is invertible.
+    // TODO(shawnsingh): Some uninvertible transforms may be visible, but
+    // their behaviour is undefined thoughout the compositor. Make their
+    // behaviour well-defined and allow the visible content rect to be non-
+    // empty when needed.
+    return gfx::Rect();
   }
+
   gfx::Rect layer_rect = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
       surface_to_layer, gfx::RectF(minimal_surface_rect)));
   layer_rect.Intersect(layer_bound_rect);
   return layer_rect;
 }
 
 gfx::Rect LayerTreeHostCommon::CalculateVisibleRect(
     gfx::Rect target_surface_rect,
     gfx::Rect layer_bound_rect,
     const gfx::Transform& transform) {
@@ skipping 1504 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