Issue: when the SDK gets (re)loaded, the uiRootNode changes
in the UiTreeBlock. However the TreeViewer is using a
content provider which root node was not updated. The fix is
to make the content provider dynamically ask for the root
node to the tree block. Instead of depending on the class
directly, a new interface is passed for this.
BUG=1761064
Automated import of CL 145004
0a7d0399c6