Remove many unused files from //skia/ext

skia/ext/convolver_mips_dspr2.h

-// Copyright (c) 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef SKIA_EXT_CONVOLVER_MIPS_DSPR2_H_
-#define SKIA_EXT_CONVOLVER_MIPS_DSPR2_H_
-
-#include "skia/ext/convolver.h"
-
-namespace skia {
-
-void ConvolveVertically_mips_dspr2(const ConvolutionFilter1D::Fixed* filter_val,
-                                   int filter_length,
-                                   unsigned char* const* source_data_rows,
-                                   int pixel_width,
-                                   unsigned char* out_row,
-                                   bool has_alpha);
-
-void ConvolveHorizontally_mips_dspr2(const unsigned char* src_data,
-                                     const ConvolutionFilter1D& filter,
-                                     unsigned char* out_row,
-                                     bool has_alpha);
-}  // namespace skia
-
-#endif  // SKIA_EXT_CONVOLVER_MIPS_DSPR2_H_