enforce 16byte alignment in shader contexts

src/core/SkEmptyShader.h

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkEmptyShader_DEFINED
 #define SkEmptyShader_DEFINED
 
 #include "SkShader.h"
 
 // TODO: move this to private, as there is a public factory on SkShader
 
 /**
  *  \class SkEmptyShader
  *  A Shader that always draws nothing. Its createContext always returns nullptr.
  */
 class SK_API SkEmptyShader : public SkShader {
 public:
     SkEmptyShader() {}
 
-    size_t contextSize(const ContextRec&) const override {
-        // Even though createContext returns nullptr we have to return a value of at least
-        // sizeof(SkShader::Context) to satisfy SkSmallAllocator.
-        return sizeof(SkShader::Context);
-    }
-
     SK_TO_STRING_OVERRIDE()
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkEmptyShader)
 
 protected:
+    size_t onContextSize(const ContextRec&) const override {
+        // Even though createContext returns nullptr we have to return a value of at least
+        // sizeof(SkShader::Context) to satisfy SkSmallAllocator.
+        return SkAlign16(sizeof(SkShader::Context));
+    }
+
     SkShader::Context* onCreateContext(const ContextRec&, void*) const override {
         return nullptr;
     }
 
     void flatten(SkWriteBuffer& buffer) const override {
         // Do nothing.
         // We just don't want to fall through to SkShader::flatten(),
         // which will write data we don't care to serialize or decode.
     }
 
 private:
     typedef SkShader INHERITED;
 };
 
 #endif