Fix dest == src bugs in Matrix.cpp.

The main bug was that the AutoJavaFloatArray autoSrc was not passing in
read only. This meant that the destructor overwrote the data which
the autoDst AutoJavaFloatArray had written in it's destructor.
This case only happened if src == dest and the arrays were copies.
Also improved performance by passing in read only a few other places.

Bug: 12570144

Change-Id: Idc8764087dc165433c584b87a0f9d4ed0ec795e8