da4abce2d9
Usually, we name methods as `GetFoo()` if they may return `nullptr`, on the other hand, we name methods as `Foo()` if they won't return `nullptr`. `RangeBoundaryBase::Container()` may return `nullptr`. So, this name may cause misleading of some developers. Let's rename it as `GetContainer()`. This does not change anything for avoiding merge conflict with the other landings. Differential Revision: https://phabricator.services.mozilla.com/D236796