Revert of Revert[2] of add ImageShader, sharing code with its Bitmap cousin

src/image/SkImageShader.h

Index: src/image/SkImageShader.h
diff --git a/src/image/SkImageShader.h b/src/image/SkImageShader.h
deleted file mode 100644
index fdd7976aad5aa2cf207fe5c7ce56402b93bd6cd6..0000000000000000000000000000000000000000
--- a/src/image/SkImageShader.h
+++ /dev/null
@@ -1,44 +0,0 @@
-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkImageShader_DEFINED
-#define SkImageShader_DEFINED
-
-#include "SkImage.h"
-#include "SkShader.h"
-
-class SkImageShader : public SkShader {
-public:
-    static SkShader* Create(const SkImage*, TileMode tx, TileMode ty, const SkMatrix* localMatrix);
-
-    bool isOpaque() const override;
-    size_t contextSize() const override;
-
-    SK_TO_STRING_OVERRIDE()
-    SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkImageShader)
-
-#if SK_SUPPORT_GPU
-    const GrFragmentProcessor* asFragmentProcessor(GrContext*, const SkMatrix& viewM,
-                                                   const SkMatrix*, SkFilterQuality,
-                                                   GrProcessorDataManager*) const override;
-#endif
-
-protected:
-    void flatten(SkWriteBuffer&) const override;
-    Context* onCreateContext(const ContextRec&, void* storage) const override;
-
-    SkAutoTUnref<const SkImage> fImage;
-    const TileMode              fTileModeX;
-    const TileMode              fTileModeY;
-
-private:
-    SkImageShader(const SkImage*, TileMode tx, TileMode ty, const SkMatrix* localMatrix);
-
-    typedef SkShader INHERITED;
-};
-
-#endif