Add all remaining separable xfer modes to GPU backend.

src/gpu/gl/GrGLSL_impl.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrGLSL_impl_DEFINED
 #define GrGLSL_impl_DEFINED
 
@@ skipping 171 matching lines @@
     } else {
         outAppend->appendf("(%s(%s) - %s(%s))",
                            GrGLSLFloatVectorTypeString(N),
                            in0,
                            GrGLSLFloatVectorTypeString(N),
                            in1);
         return kNone_GrSLConstantVec;
     }
 }
 
-
 #endif