S4 only has 8 texture units on the GLContext we create

bench/GLBench.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GLBench.h"
 
 #if SK_SUPPORT_GPU
@@ skipping 92 matching lines @@
     GR_GL_CALL(gl, DeleteShader(vertexShader));
     GR_GL_CALL(gl, DeleteShader(fragmentShader));
 
     return shaderProgram;
 }
 
 GrGLuint GLBench::SetupFramebuffer(const GrGLInterface* gl, int screenWidth, int screenHeight) {
     //Setup framebuffer
     GrGLuint texture;
     GR_GL_CALL(gl, GenTextures(1, &texture));
-    GR_GL_CALL(gl, ActiveTexture(GR_GL_TEXTURE15));
+    GR_GL_CALL(gl, ActiveTexture(GR_GL_TEXTURE7));
     GR_GL_CALL(gl, BindTexture(GR_GL_TEXTURE_2D, texture));
     GR_GL_CALL(gl, TexParameteri(GR_GL_TEXTURE_2D, GR_GL_TEXTURE_MAG_FILTER, GR_GL_NEAREST));
     GR_GL_CALL(gl, TexParameteri(GR_GL_TEXTURE_2D, GR_GL_TEXTURE_MIN_FILTER, GR_GL_NEAREST));
     GR_GL_CALL(gl, TexParameteri(GR_GL_TEXTURE_2D, GR_GL_TEXTURE_WRAP_S, GR_GL_CLAMP_TO_EDGE));
     GR_GL_CALL(gl, TexParameteri(GR_GL_TEXTURE_2D, GR_GL_TEXTURE_WRAP_T, GR_GL_CLAMP_TO_EDGE));
     GR_GL_CALL(gl, TexImage2D(GR_GL_TEXTURE_2D,
                               0, //level
                               GR_GL_RGBA, //internal format
                               screenWidth, // width
                               screenHeight, // height
@@ skipping 39 matching lines @@
     bm.setPixels(readback.get());
 
     if (!SkImageEncoder::EncodeFile(filename, bm, SkImageEncoder::kPNG_Type, 100)) {
         SkDebugf("------ failed to encode %s\n", filename);
         remove(filename);   // remove any partial file
         return;
     }
 }
 
 #endif