Stop referencing gl_FragCoord z and w components.

src/gpu/effects/GrDitherEffect.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "GrDitherEffect.h"
 
 #include "gl/GrGLEffect.h"
@@ skipping 84 matching lines @@
     // Generate a random number based on the fragment position. For this
     // random number generator, we use the "GLSL rand" function
     // that seems to be floating around on the internet. It works under
     // the assumption that sin(<big number>) oscillates with high frequency
     // and sampling it will generate "randomness". Since we're using this
     // for rendering and not cryptography it should be OK.
 
     // For each channel c, add the random offset to the pixel to either bump
     // it up or let it remain constant during quantization.
     builder->fsCodeAppendf("\t\tfloat r = "
-                           "fract(sin(dot(%s.xy ,vec2(12.9898,78.233))) * 43758.5453);\n",
+                           "fract(sin(dot(%s ,vec2(12.9898,78.233))) * 43758.5453);\n",
                            builder->fragmentPosition());
     builder->fsCodeAppendf("\t\t%s = (1.0/255.0) * vec4(r, r, r, r) + %s;\n",
                            outputColor, GrGLSLExpr4(inputColor).c_str());
 }
 
 //////////////////////////////////////////////////////////////////////////////
 
 GrEffectRef* GrDitherEffect::Create() {
     return DitherEffect::Create();
 }