Possible fix for Moto E compilation failure

src/gpu/gl/builders/GrGLFragmentShaderBuilder.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 "GrGLFragmentShaderBuilder.h"
 #include "GrGLProgramBuilder.h"
 #include "gl/GrGLGpu.h"
@@ skipping 141 matching lines @@
             }
             fInputs.push_back().set(kVec4f_GrSLType,
                                     GrGLShaderVar::kIn_TypeModifier,
                                     "gl_FragCoord",
                                     kDefault_GrSLPrecision,
                                     GrGLShaderVar::kUpperLeft_Origin);
             fSetupFragPosition = true;
         }
         return "gl_FragCoord";
     } else {
+        static const char* kTempName = "tmpXYFragCoord";
         static const char* kCoordName = "fragCoordYDown";
         if (!fSetupFragPosition) {
             // temporarily change the stage index because we're inserting non-stage code.
             GrGLProgramBuilder::AutoStageRestore asr(fProgramBuilder);
             SkASSERT(!fProgramBuilder->fUniformHandles.fRTHeightUni.isValid());
             const char* rtHeightName;
 
             fProgramBuilder->fUniformHandles.fRTHeightUni =
                     fProgramBuilder->addUniform(GrGLProgramBuilder::kFragment_Visibility,
                                                 kFloat_GrSLType,
                                                 kDefault_GrSLPrecision,
                                                 "RTHeight",
                                                 &rtHeightName);
 
-            // Using glFragCoord.zw for the last two components tickles an Adreno driver bug that
-            // causes programs to fail to link. Making this function return a vec2() didn't fix the
-            // problem but using 1.0 for the last two components does.
-            this->codePrependf("\tvec4 %s = vec4(gl_FragCoord.x, %s - gl_FragCoord.y, 1.0, "
-                               "1.0);\n", kCoordName, rtHeightName);
+            // The Adreno compiler seems to be very touchy about access to "gl_FragCoord".
+            // Accessing glFragCoord.zw can cause a program to fail to link. Additionally,
+            // depending on the surrounding code, accessing .xy with a uniform involved can
+            // do the same thing. Copying gl_FragCoord.xy into a temp vec2 beforehand 
+            // (and only accessing .xy) seems to "fix" things.
+            this->codePrependf("\tvec4 %s = vec4(%s.x, %s - %s.y, 1.0, 1.0);\n",
+                               kCoordName, kTempName, rtHeightName, kTempName);
+            this->codePrependf("vec2 %s = gl_FragCoord.xy;", kTempName);
             fSetupFragPosition = true;
         }
         SkASSERT(fProgramBuilder->fUniformHandles.fRTHeightUni.isValid());
         return kCoordName;
     }
 }
 
 const char* GrGLFragmentShaderBuilder::dstColor() {
     fHasReadDstColor = true;
 
@@ skipping 83 matching lines @@
     }
 }
 
 void GrGLFragmentShaderBuilder::addVarying(GrGLVarying* v, GrSLPrecision fsPrec) {
     v->fFsIn = v->fVsOut;
     if (v->fGsOut) {
         v->fFsIn = v->fGsOut;
     }
     fInputs.push_back().set(v->fType, GrGLShaderVar::kVaryingIn_TypeModifier, v->fFsIn, fsPrec);
 }