Use noperspective interpolation for 2D draws

src/gpu/glsl/GrGLSLShaderVar.h

Index: src/gpu/glsl/GrGLSLShaderVar.h
diff --git a/src/gpu/glsl/GrGLSLShaderVar.h b/src/gpu/glsl/GrGLSLShaderVar.h
index e26a75c0966794143980f48a66b7755f823bd806..812d604be9150de9aca1968fc1a1cf3090f35c02 100644
--- a/src/gpu/glsl/GrGLSLShaderVar.h
+++ b/src/gpu/glsl/GrGLSLShaderVar.h
@@ -51,7 +51,9 @@ public:
     GrGLSLShaderVar(const GrGLSLShaderVar& var)
         : GrShaderVar(var.c_str(), var.getType(), var.getTypeModifier(),
                       var.getArrayCount(), var.getPrecision())
-        , fUseUniformFloatArrays(var.fUseUniformFloatArrays) {
+        , fUseUniformFloatArrays(var.fUseUniformFloatArrays)
+        , fLayoutQualifier(var.fLayoutQualifier)
+        , fExtraModifiers(var.fExtraModifiers) {
         SkASSERT(kVoid_GrSLType != var.getType());
     }
 
@@ -136,6 +138,10 @@ public:
         fLayoutQualifier = layoutQualifier;
     }
 
+    void addModifier(const char* modifier) {
+        fExtraModifiers.appendf("%s ", modifier);
+    }
+
     /**
      * Write a declaration of this variable to out.
      */
@@ -144,11 +150,8 @@ public:
         if (!fLayoutQualifier.isEmpty()) {
             out->appendf("layout(%s) ", fLayoutQualifier.c_str());
         }
+        out->append(fExtraModifiers);
         if (this->getTypeModifier() != kNone_TypeModifier) {
-            if (GrSLTypeIsIntType(fType) && (this->getTypeModifier() == kVaryingIn_TypeModifier ||
-                                             this->getTypeModifier() == kVaryingOut_TypeModifier)) {
-                out->append("flat ");
-            }
             out->append(TypeModifierString(glslCaps, this->getTypeModifier()));
             out->append(" ");
         }
@@ -234,9 +237,10 @@ private:
 
     /// Work around driver bugs on some hardware that don't correctly
     /// support uniform float []
-    bool            fUseUniformFloatArrays;
+    bool        fUseUniformFloatArrays;
 
-    SkString        fLayoutQualifier;
+    SkString    fLayoutQualifier;
+    SkString    fExtraModifiers;
 
     typedef GrShaderVar INHERITED;
 };