Refactor GrGLUniformManager::UniformHandle to initialize itself by default

src/gpu/effects/GrConvolutionEffect.cpp

Index: src/gpu/effects/GrConvolutionEffect.cpp
diff --git a/src/gpu/effects/GrConvolutionEffect.cpp b/src/gpu/effects/GrConvolutionEffect.cpp
index e7fb8e5403d9c6bc60c6f2a923d252c83e757b6d..65da81111b98ef3ddf2f5367058ac52597750e0a 100644
--- a/src/gpu/effects/GrConvolutionEffect.cpp
+++ b/src/gpu/effects/GrConvolutionEffect.cpp
@@ -14,7 +14,6 @@
 
 // For brevity
 typedef GrGLUniformManager::UniformHandle UniformHandle;
-static const UniformHandle kInvalidUniformHandle = GrGLUniformManager::kInvalidUniformHandle;
 
 class GrGLConvolutionEffect : public GrGLEffect {
 public:
@@ -50,9 +49,6 @@ private:
 GrGLConvolutionEffect::GrGLConvolutionEffect(const GrBackendEffectFactory& factory,
                                              const GrDrawEffect& drawEffect)
     : INHERITED(factory)
-    , fKernelUni(kInvalidUniformHandle)
-    , fImageIncrementUni(kInvalidUniformHandle)
-    , fBoundsUni(kInvalidUniformHandle)
     , fEffectMatrix(drawEffect.castEffect<GrConvolutionEffect>().coordsType()) {
     const GrConvolutionEffect& c = drawEffect.castEffect<GrConvolutionEffect>();
     fRadius = c.radius();