Fix null check for BaseObj.equals.

Change-Id: I4f060697db175cbf0b5617c1220db853bbe53f1f
Avoid duplication of AppWindowToken in created Task

When WindowManagerService creates a new Task, it passes atoken to the
Task constructor. In this case atoken is added to mAppTokens list by
the Task constructor and then it is added manually again by calling
newTask.mAppTokens.add(atoken). As a result, the same atoken is present
in mAppTokens list twice.

When another window token is added to the list, it may be placed in
beetwen duplicated tokens and corresponding window will be hidden from
the screen by corresponding duplicated windows.
From user perspective it means that some windows will not be displayed
on the screen.

The issue is fixed by avoid adding atoken to mAppTokens list manually
when it was added already in Task constructor.

Change-Id: I10628e68186160fffdde07beb7d84ab3cecb7051
Fix: Linked volumes

Check for linked volumes a little earlier than we previously did.
This ensures the correct value is set after boot.

Change-Id: I207680bed1b849351d6cbb283ae415621fab58b4
core: bring original volume panel expand icon back

This one makes more sense from a UX standpoint
Update the color of the expandable volume panel icon

This still retains the old settings icon since it
happens to fit perfectly. Pressing it does indeed
show you a bunch of sliders like the icon indicates.

Also add xhdpi and xxhdpi versions.