Changing texture to have a virtual destructor.
Changing texture to have a virtual destructor.

Since Texture has virtual functions, it should have a virtual
destructor.

Tested on Linux and Android.

Change-Id: I505fcca414a86ecb1fc4c5245b5975cedb8e1008

google/fplbase,google/fplbase,google/fplbase,google/fplbase