Clean LayerImpl's scroll offset callers in unit tests.

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 <stddef.h>
 
 #include <map>
 #include <set>
@@ skipping 654 matching lines @@
       main_thread_scrolling_reasons !=
       data_from_ancestor.main_thread_scrolling_reasons;
   bool requires_node =
       scroll_node_uninheritable_criteria ||
       (main_thread_scrolling_reasons !=
            MainThreadScrollingReason::kNotScrollingOnMain &&
        (has_different_main_thread_scrolling_reasons ||
         data_from_ancestor
             .scroll_tree_parent_created_by_uninheritable_criteria));
 
+  // Remove the entry from scroll_offset_map
+  if (!scrollable)
+    data_for_children->scroll_tree->scroll_offset_map().erase(layer->id());

[ajuma, 2016/03/07 19:10:19]

Is this only needed for tests? If so, please add a comment explaining. If it's
actually needed for non-test code, please also add a test.

[sunxd, 2016/03/09 01:51:21]

Done.

+
   if (!requires_node) {
     data_for_children->scroll_tree_parent = parent_id;
   } else {
     ScrollNode node;
     node.owner_id = layer->id();
     node.data.scrollable = scrollable;
     node.data.main_thread_scrolling_reasons = main_thread_scrolling_reasons;
     node.data.contains_non_fast_scrollable_region =
         contains_non_fast_scrollable_region;
     gfx::Size clip_bounds;
@@ skipping 309 matching lines @@
   if (SkColorGetA(color) != 255)
     color = SkColorSetA(color, 255);
   BuildPropertyTreesTopLevelInternal(
       root_layer, page_scale_layer, inner_viewport_scroll_layer,
       outer_viewport_scroll_layer, overscroll_elasticity_layer,
       elastic_overscroll, page_scale_factor, device_scale_factor, viewport,
       device_transform, property_trees, color);
 }
 
 }  // namespace cc