Add gpu backend for SkPixelXorXfermode

src/gpu/GrProcessor.cpp

Index: src/gpu/GrProcessor.cpp
diff --git a/src/gpu/GrProcessor.cpp b/src/gpu/GrProcessor.cpp
index 1db9d76fda34bd0006fa4d866ae1de83bfeb2eb5..20f7d7205b3c6d67ecc3b62e21b662cc302bb856 100644
--- a/src/gpu/GrProcessor.cpp
+++ b/src/gpu/GrProcessor.cpp
@@ -48,9 +48,9 @@ GrProcessorTestFactory<GrGeometryProcessor>::GetFactories() {
  * we verify the count is as expected.  If a new factory is added, then these numbers must be
  * manually adjusted.
  */
-static const int kFPFactoryCount = 38;
+static const int kFPFactoryCount = 39;
 static const int kGPFactoryCount = 14;
-static const int kXPFactoryCount = 5;
+static const int kXPFactoryCount = 6;
 
 template<>
 void GrProcessorTestFactory<GrFragmentProcessor>::VerifyFactoryCount() {