Remove SkShader virtual method validContext

patch from issue 267923005

BUG=skia:
R=scroggo@google.com

Author: reed@google.com

Review URL: https://codereview.chromium.org/261773005

git-svn-id: http://skia.googlecode.com/svn/trunk@14573 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/effects/gradients/SkTwoPointConicalGradient.cpp b/src/effects/gradients/SkTwoPointConicalGradient.cpp
index e9c2efe..574df08 100644
--- a/src/effects/gradients/SkTwoPointConicalGradient.cpp
+++ b/src/effects/gradients/SkTwoPointConicalGradient.cpp
@@ -221,12 +221,8 @@
     return sizeof(TwoPointConicalGradientContext);
 }
 
-SkShader::Context* SkTwoPointConicalGradient::createContext(const ContextRec& rec,
-                                                            void* storage) const {
-    if (!this->validContext(rec)) {
-        return NULL;
-    }
-
+SkShader::Context* SkTwoPointConicalGradient::onCreateContext(const ContextRec& rec,
+                                                              void* storage) const {
     return SkNEW_PLACEMENT_ARGS(storage, TwoPointConicalGradientContext, (*this, rec));
 }