Update from https://crrev.com/320343

cc/trees/property_tree_builder.cc

 // Copyright 2014 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/property_tree_builder.h"
 
 #include <map>
 #include <set>
 
 #include "cc/base/math_util.h"
@@ skipping 15 matching lines @@
   Layer* transform_fixed_parent;
   Layer* render_target;
   int clip_tree_parent;
   int opacity_tree_parent;
   gfx::Vector2dF offset_to_transform_tree_parent;
   gfx::Vector2dF offset_to_transform_fixed_parent;
   const Layer* page_scale_layer;
   float page_scale_factor;
   float device_scale_factor;
   bool in_subtree_of_page_scale_application_layer;
+  bool should_flatten;
   const gfx::Transform* device_transform;
 };
 
 static Layer* GetTransformParent(const DataForRecursion& data, Layer* layer) {
   return layer->position_constraint().is_fixed_position()
              ? data.transform_fixed_parent
              : data.transform_tree_parent;
 }
 
 static ClipNode* GetClipParent(const DataForRecursion& data, Layer* layer) {
@@ skipping 71 matching lines @@
 
   const bool has_significant_transform =
       !layer->transform().IsIdentityOr2DTranslation();
 
   const bool has_animated_transform =
       layer->layer_animation_controller()->IsAnimatingProperty(
           Animation::TRANSFORM);
 
   const bool has_surface = !!layer->render_surface();
 
-  const bool flattening_change = layer->parent() &&
-                                 layer->should_flatten_transform() &&
-                                 !layer->parent()->should_flatten_transform();
-
   bool requires_node = is_root || is_scrollable || has_significant_transform ||
                        has_animated_transform || has_surface ||
-                       is_page_scale_application_layer || flattening_change;
+                       is_page_scale_application_layer;
 
   Layer* transform_parent = GetTransformParent(data_from_ancestor, layer);
 
   // May be non-zero if layer is fixed or has a scroll parent.
   gfx::Vector2dF parent_offset;
   if (transform_parent) {
     // TODO(vollick): This is to mimic existing bugs (crbug.com/441447).
     if (!is_fixed) {
       parent_offset = transform_parent->offset_to_transform_parent();
     } else if (data_from_ancestor.transform_tree_parent !=
@@ skipping 21 matching lines @@
         transform_parent->transform_tree_index(), &to_parent);
 
     parent_offset += to_parent.To2dTranslation();
   }
 
   if (layer->IsContainerForFixedPositionLayers() || is_root)
     data_for_children->transform_fixed_parent = layer;
   data_for_children->transform_tree_parent = layer;
 
   if (!requires_node) {
+    data_for_children->should_flatten |= layer->should_flatten_transform();
     gfx::Vector2dF local_offset = layer->position().OffsetFromOrigin() +
                                   layer->transform().To2dTranslation();
     layer->set_offset_to_transform_parent(parent_offset + local_offset);
     layer->set_transform_tree_index(transform_parent->transform_tree_index());
     return;
   }
 
   int parent_index = 0;
   if (transform_parent)
     parent_index = transform_parent->transform_tree_index();
 
   data_for_children->transform_tree->Insert(TransformNode(), parent_index);
 
   TransformNode* node = data_for_children->transform_tree->back();
   layer->set_transform_tree_index(node->id);
 
   node->data.scrolls = is_scrollable;
-  node->data.flattens = layer->should_flatten_transform();
+  node->data.flattens_inherited_transform = data_for_children->should_flatten;
+  node->data.flattens_local_transform = layer->should_flatten_transform();
+  data_for_children->should_flatten = false;
   node->data.target_id =
       data_from_ancestor.render_target->transform_tree_index();
   node->data.content_target_id =
       data_for_children->render_target->transform_tree_index();
   DCHECK_NE(node->data.target_id, -1);
   node->data.is_animated = layer->TransformIsAnimating();
 
   float scale_factors = 1.0f;
   if (is_root) {
     node->data.post_local = *data_from_ancestor.device_transform;
@@ skipping 106 matching lines @@
   data_for_recursion.opacity_tree = opacity_tree;
   data_for_recursion.transform_tree_parent = nullptr;
   data_for_recursion.transform_fixed_parent = nullptr;
   data_for_recursion.render_target = root_layer;
   data_for_recursion.clip_tree_parent = 0;
   data_for_recursion.opacity_tree_parent = -1;
   data_for_recursion.page_scale_layer = page_scale_layer;
   data_for_recursion.page_scale_factor = page_scale_factor;
   data_for_recursion.device_scale_factor = device_scale_factor;
   data_for_recursion.in_subtree_of_page_scale_application_layer = false;
+  data_for_recursion.should_flatten = false;
   data_for_recursion.device_transform = &device_transform;
 
   ClipNode root_clip;
   root_clip.data.clip = viewport;
   root_clip.data.transform_id = 0;
   data_for_recursion.clip_tree_parent = clip_tree->Insert(root_clip, 0);
   BuildPropertyTreesInternal(root_layer, data_for_recursion);
 }
 
 }  // namespace cc