Make startDrag protected.

CL I62688119eafd8bbc4760236c0f4b453dca74dc80 changed the visibility of
startDrag from package to private. However the method is used by a child
class of TaskPositioner.

The CL changes the visibility of startDrag to protected.

Bug: None
Test: make
Merged-In: I7d827d639a681eec9f8fbbd5fd976710d87cf1cc
Change-Id: I7d827d639a681eec9f8fbbd5fd976710d87cf1cc
1 file changed