Bug 969460 part 1: Give EnsureBlockDisplay a second parameter, to determine whether it converts 'display:list-item' to block. r=bz
Bug 969460 part 2: Use EnsureBlockDisplay to determine the 'display' of the root node, and let nsCSSFrameConstructor::ConstructDocElementFrame create flex containers. r=bz
Bug 969460 part 3: regression tests for "display:flex" on root node. r=bz