Revert[4] of add ImageShader, sharing code with its Bitmap cousin

Now with GrTextureMaker subclasses to handle npot usage.

This reverts commit 476506d070dbc59b158acc1a00c34bff95ab2968.

BUG=skia:

Review URL: https://codereview.chromium.org/1370223002
diff --git a/src/image/SkImage_Base.h b/src/image/SkImage_Base.h
index bbcf182..757262a 100644
--- a/src/image/SkImage_Base.h
+++ b/src/image/SkImage_Base.h
@@ -54,11 +54,8 @@
     // Caller must call unref when they are done.
     virtual GrTexture* asTextureRef(GrContext*, SkImageUsageType) const = 0;
 
-    virtual SkShader* onNewShader(SkShader::TileMode,
-                                  SkShader::TileMode,
-                                  const SkMatrix* localMatrix) const { return nullptr; }
-
     virtual SkImage* onNewSubset(const SkIRect&) const = 0;
+
     virtual SkData* onRefEncoded() const { return nullptr; }
 
     virtual bool onAsLegacyBitmap(SkBitmap*, LegacyBitmapMode) const;