Don't use magic statics in SincResampler for thread safe init.

media/base/sinc_resampler.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 MEDIA_BASE_SINC_RESAMPLER_H_
 #define MEDIA_BASE_SINC_RESAMPLER_H_
 
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/aligned_memory.h"
@@ skipping 55 matching lines @@
  private:
   FRIEND_TEST_ALL_PREFIXES(SincResamplerTest, Convolve);
   FRIEND_TEST_ALL_PREFIXES(SincResamplerTest, ConvolveBenchmark);
 
   void InitializeKernel();
 
   // Compute convolution of |k1| and |k2| over |input_ptr|, resultant sums are
   // linearly interpolated using |kernel_interpolation_factor|.  On x86, the
   // underlying implementation is chosen at run time based on SSE support.  On
   // ARM, NEON support is chosen at compile time based on compilation flags.
-  static float Convolve(const float* input_ptr, const float* k1,
-                        const float* k2, double kernel_interpolation_factor);
   static float Convolve_C(const float* input_ptr, const float* k1,
                           const float* k2, double kernel_interpolation_factor);
 #if defined(ARCH_CPU_X86_FAMILY)
   static float Convolve_SSE(const float* input_ptr, const float* k1,
                             const float* k2,
                             double kernel_interpolation_factor);
 #elif defined(ARCH_CPU_ARM_FAMILY) && defined(USE_NEON)
   static float Convolve_NEON(const float* input_ptr, const float* k1,
                              const float* k2,
                              double kernel_interpolation_factor);
@@ skipping 13 matching lines @@
   ReadCB read_cb_;
 
   // Contains kKernelOffsetCount kernels back-to-back, each of size kKernelSize.
   // The kernel offsets are sub-sample shifts of a windowed sinc shifted from
   // 0.0 to 1.0 sample.
   scoped_ptr_malloc<float, base::ScopedPtrAlignedFree> kernel_storage_;
 
   // Data from the source is copied into this buffer for each processing pass.
   scoped_ptr_malloc<float, base::ScopedPtrAlignedFree> input_buffer_;
 
+  // Stores the runtime selection of which Convolve function to use.
+#if defined(ARCH_CPU_X86_FAMILY) && !defined(__SSE__)
+  typedef float (*ConvolveProc)(const float*, const float*, const float*,
+                                double);
+  const ConvolveProc convolve_proc_;
+#endif
+
   // Pointers to the various regions inside |input_buffer_|.  See the diagram at
   // the top of the .cc file for more information.
   float* const r0_;
   float* const r1_;
   float* const r2_;
   float* const r3_;
   float* const r4_;
   float* const r5_;
 
   DISALLOW_COPY_AND_ASSIGN(SincResampler);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_SINC_RESAMPLER_H_