Add View methods isAttachedToWindow and hasLayout

isAttachedToWindow does what it says on the label and provides a
standard, public API for checking a view's attachment state. This
removes the need for tracking this out of band in response to
onAttachedToWindow/onDetachedFromWindow in custom view
implementations.

hasLayout returns true whenever the view has been through at least one
call to layout() since the last time it was attached to or detached
from a window. This allows for standard checks in code that needs to
behave differently if first layout has not completed yet, such as
whether or not to no-op an animation in order to set up initial state.

Change-Id: I8dab70dcd5a22a32e260ed50987ccdaa4100072b