Remove backend factories

BUG=skia:

Review URL: https://codereview.chromium.org/778453002
diff --git a/src/effects/gradients/SkGradientShader.cpp b/src/effects/gradients/SkGradientShader.cpp
index e70be04..f3e5131 100644
--- a/src/effects/gradients/SkGradientShader.cpp
+++ b/src/effects/gradients/SkGradientShader.cpp
@@ -887,13 +887,11 @@
 
 #include "effects/GrTextureStripAtlas.h"
 #include "GrInvariantOutput.h"
-#include "GrTBackendProcessorFactory.h"
 #include "gl/builders/GrGLProgramBuilder.h"
 #include "SkGr.h"
 
-GrGLGradientEffect::GrGLGradientEffect(const GrBackendProcessorFactory& factory)
-    : INHERITED(factory)
-    , fCachedYCoord(SK_ScalarMax) {
+GrGLGradientEffect::GrGLGradientEffect()
+    : fCachedYCoord(SK_ScalarMax) {
 }
 
 GrGLGradientEffect::~GrGLGradientEffect() { }