Refactor GrGLUniformManager::UniformHandle to initialize itself by default

src/effects/SkMagnifierImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkMagnifierImageFilter.h"
 #include "SkColorPriv.h"
@@ skipping 100 matching lines @@
     UniformHandle       fInsetVar;
 
     GrGLEffectMatrix    fEffectMatrix;
 
     typedef GrGLEffect INHERITED;
 };
 
 GrGLMagnifierEffect::GrGLMagnifierEffect(const GrBackendEffectFactory& factory,
                                          const GrDrawEffect& drawEffect)
     : INHERITED(factory)
-    , fOffsetVar(GrGLUniformManager::kInvalidUniformHandle)
-    , fZoomVar(GrGLUniformManager::kInvalidUniformHandle)
-    , fInsetVar(GrGLUniformManager::kInvalidUniformHandle)
     , fEffectMatrix(drawEffect.castEffect<GrMagnifierEffect>().coordsType()) {
 }
 
 void GrGLMagnifierEffect::emitCode(GrGLShaderBuilder* builder,
                                    const GrDrawEffect&,
                                    EffectKey key,
                                    const char* outputColor,
                                    const char* inputColor,
                                    const TextureSamplerArray& samplers) {
     const char* coords;
@@ skipping 211 matching lines @@
 
             int x_val = SkMin32(SkScalarFloorToInt(x_interp), width - 1);
             int y_val = SkMin32(SkScalarFloorToInt(y_interp), height - 1);
 
             *dptr = sptr[y_val * width + x_val];
             dptr++;
         }
     }
     return true;
 }