Clean LayerImpl's scroll offset callers in unit tests.

cc/trees/property_tree_builder.cc

Index: cc/trees/property_tree_builder.cc
diff --git a/cc/trees/property_tree_builder.cc b/cc/trees/property_tree_builder.cc
index 14338a4cd304020f7bc44b80bedb764a4b972271..4096d335907fef086b98f6b69d1f014585869259 100644
--- a/cc/trees/property_tree_builder.cc
+++ b/cc/trees/property_tree_builder.cc
@@ -672,6 +672,10 @@ void AddScrollNodeIfNeeded(
         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 {