Refactor GrGLUniformManager::UniformHandle to initialize itself by default

src/effects/SkColorMatrixFilter.cpp

Index: src/effects/SkColorMatrixFilter.cpp
diff --git a/src/effects/SkColorMatrixFilter.cpp b/src/effects/SkColorMatrixFilter.cpp
index 3d1fd6f62749ee3350a1ebb4df4364bbf2875310..7bb9673d10a16ec80ad503aa914f505a4c8dc1b0 100644
--- a/src/effects/SkColorMatrixFilter.cpp
+++ b/src/effects/SkColorMatrixFilter.cpp
@@ -391,9 +391,8 @@ public:
 
         GLEffect(const GrBackendEffectFactory& factory,
                  const GrDrawEffect&)
-        : INHERITED(factory)
-        , fMatrixHandle(GrGLUniformManager::kInvalidUniformHandle)
-        , fVectorHandle(GrGLUniformManager::kInvalidUniformHandle) {}
+        : INHERITED(factory) {
+        }
 
         virtual void emitCode(GrGLShaderBuilder* builder,
                               const GrDrawEffect&,