Remove SkShader virtual method validContext

src/effects/SkTransparentShader.cpp

Index: src/effects/SkTransparentShader.cpp
diff --git a/src/effects/SkTransparentShader.cpp b/src/effects/SkTransparentShader.cpp
index 9a390ad6f299f5258579030f9d8abd2dad2d104e..f290d0dcf8d5c0b834b8729e519661f302f31799 100644
--- a/src/effects/SkTransparentShader.cpp
+++ b/src/effects/SkTransparentShader.cpp
@@ -11,11 +11,8 @@
 #include "SkColorPriv.h"
 #include "SkString.h"
 
-SkShader::Context* SkTransparentShader::createContext(const ContextRec& rec, void* storage) const {
-    if (!this->validContext(rec)) {
-        return NULL;
-    }
-
+SkShader::Context* SkTransparentShader::onCreateContext(const ContextRec& rec,
+                                                        void* storage) const {
     return SkNEW_PLACEMENT_ARGS(storage, TransparentShaderContext, (*this, rec));
 }