Fix potential inconsistent DragLayout state

Prior to this change is was possible for DragLayout to end up in an open
state without a visible HistoryFragment. With this change we only enter
an open state after a successful view capture.

Fixes: 34157451
Test: manually verified on API 21, 23 & 25 device
Change-Id: Ia3631692ccc4281d06fd53f9b926e3043a9827f1