Remove many unused files from //skia/ext

skia/ext/convolver_SSE2.h

-// Copyright (c) 2012 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_SSE2_H_
-#define SKIA_EXT_CONVOLVER_SSE2_H_
-
-#include "skia/ext/convolver.h"
-
-namespace skia {
-
-void ConvolveVertically_SSE2(const ConvolutionFilter1D::Fixed* filter_values,
-                             int filter_length,
-                             unsigned char* const* source_data_rows,
-                             int pixel_width,
-                             unsigned char* out_row,
-                             bool has_alpha);
-void Convolve4RowsHorizontally_SSE2(const unsigned char* src_data[4],
-                                    const ConvolutionFilter1D& filter,
-                                    unsigned char* out_row[4]);
-void ConvolveHorizontally_SSE2(const unsigned char* src_data,
-                               const ConvolutionFilter1D& filter,
-                               unsigned char* out_row,
-                               bool has_alpha);
-}  // namespace skia
-
-#endif  // SKIA_EXT_CONVOLVER_SSE2_H_