Stop displaying layers with non-invertible transforms.

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index 4dc35522a28d6ca42ad70936f73eedb5b48ac3d8..6b9241d554c79bd0b8bc0abaef185b944b61de1a 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -478,6 +478,10 @@ static bool LayerShouldBeSkipped(LayerType* layer, bool layer_is_drawn) {
 
 static inline bool SubtreeShouldBeSkipped(LayerImpl* layer,
                                           bool layer_is_drawn) {
+  // If the layer transform is not invertible, it should not be drawn.
+  if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
+    return true;
+
   // When we need to do a readback/copy of a layer's output, we can not skip
   // it or any of its ancestors.
   if (layer->draw_properties().layer_or_descendant_has_copy_request)
@@ -501,6 +505,13 @@ static inline bool SubtreeShouldBeSkipped(LayerImpl* layer,
 }
 
 static inline bool SubtreeShouldBeSkipped(Layer* layer, bool layer_is_drawn) {
+  // If the layer transform is not invertible, it should not be drawn.
+  // TODO(ajuma): Correctly process subtrees with singular transform for the
+  // case where we may animate to a non-singular transform and wish to
+  // pre-raster.

[ajuma, 2014/04/16 19:24:49]

This TODO should move to the previous function (the LayerImpl version).

[avallee, 2014/04/16 19:33:25]

Done.

+  if (!layer->transform_is_invertible() && !layer->TransformIsAnimating())
+    return true;
+
   // When we need to do a readback/copy of a layer's output, we can not skip
   // it or any of its ancestors.
   if (layer->draw_properties().layer_or_descendant_has_copy_request)
@@ -1165,6 +1176,12 @@ static void PreCalculateMetaInformation(
   bool has_delegated_content = layer->HasDelegatedContent();
   int num_descendants_that_draw_content = 0;
 
+  if (!layer->transform_is_invertible()) {
+    // Layers with singular transforms should not be drawn, the whole subtree
+    // can be skipped.
+    return;
+  }
+
   if (has_delegated_content) {
     // Layers with delegated content need to be treated as if they have as
     // many children as the number of layers they own delegated quads for.