Implement color filter as GrGLEffect

src/effects/SkMatrixConvolutionImageFilter.cpp

Index: src/effects/SkMatrixConvolutionImageFilter.cpp
diff --git a/src/effects/SkMatrixConvolutionImageFilter.cpp b/src/effects/SkMatrixConvolutionImageFilter.cpp
index a9dfecce5918f90ae80db218eb8b2d10f4bca64a..c89b9dc63fce8711855b30e46e5b1222aaa68e8e 100644
--- a/src/effects/SkMatrixConvolutionImageFilter.cpp
+++ b/src/effects/SkMatrixConvolutionImageFilter.cpp
@@ -423,6 +423,7 @@ void GrGLMatrixConvolutionEffect::emitCode(GrGLShaderBuilder* builder,
                                            const char* inputColor,
                                            const TransformedCoordsArray& coords,
                                            const TextureSamplerArray& samplers) {
+    sk_ignore_unused_variable(inputColor);
     SkString coords2D = builder->ensureFSCoords2D(coords, 0);
     fBoundsUni = builder->addUniform(GrGLShaderBuilder::kFragment_Visibility,
                                      kVec4f_GrSLType, "Bounds");
@@ -548,6 +549,7 @@ GrMatrixConvolutionEffect::GrMatrixConvolutionEffect(GrTexture* texture,
     }
     fTarget[0] = static_cast<float>(target.x());
     fTarget[1] = static_cast<float>(target.y());
+    this->setWillNotUseInputColor();
 }
 
 GrMatrixConvolutionEffect::~GrMatrixConvolutionEffect() {