Make WidgetHierarchyUpdatesSuspensionScope use swap instead of copy

This is equivalent behavior code that is unambiguously better performance. swap is O(1) time and memory, copying a hash table is at least linear with the number of elements.

(Caveat: I don't know how big that map can get, so this may not have any noticeable impact on performance).

BUG=

Review URL: https://chromiumcodereview.appspot.com/15741010

git-svn-id: svn://svn.chromium.org/blink/trunk@150931 bbb929c8-8fbe-4397-9dbb-9b2b20218538
1 file changed