This is a follow-up to bug 117733. If the glContext() call in LayerTreeHostGtk::initialize() returns null, m_isValid is set to false, which breaks an assertion in invalidate(). It's not necessary to set m_isValid here, the rest of the code already deals with the case where glContext() is null so that can be safely removed. The m_isValid variable is otherwise relevant in this class since it checks that invalidate() is called once before the object is destroyed.
Created attachment 210789 [details] Patch
Committed r155533: <http://trac.webkit.org/changeset/155533>