libgui: Add computeTextureMatrix method to ConsumerBase

Moves the GLConsumer::computeCurrentTransformMatrixLocked
implementation to ConsumerBase::computeTextureMatrix. This allows all
classes that inherit from ConsumerBase to access the functionality.

Bug 944874
Bug 1333245

Change-Id: I688a9342ac82024303e4d5b81c5b0994304bf0eb
Reviewed-on: http://git-master/r/197190
(cherry picked from commit a1add13efc9b930605871a25219dfd3ac69ea532)
Reviewed-on: http://git-master/r/259045
Reviewed-by: Srikumar Bonda <sbonda@nvidia.com>
Tested-by: Srikumar Bonda <sbonda@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Dan Willemsen <dwillemsen@nvidia.com>