document cpuid command line behavior

include/libyuv/cpu_id.h

 /*
  *  Copyright 2011 The LibYuv Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS. All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 44 matching lines @@
 // Test_flag parameter should be one of kCpuHas constants above.
 // returns non-zero if instruction set is detected
 static __inline int TestCpuFlag(int test_flag) {
   LIBYUV_API extern int cpu_info_;
   return (!cpu_info_ ? InitCpuFlags() : cpu_info_) & test_flag;
 }
 
 // For testing, allow CPU flags to be disabled.
 // ie MaskCpuFlags(~kCpuHasSSSE3) to disable SSSE3.
 // MaskCpuFlags(-1) to enable all cpu specific optimizations.
-// MaskCpuFlags(0) to disable all cpu specific optimizations.
+// MaskCpuFlags(1) to disable all cpu specific optimizations.
 LIBYUV_API
 void MaskCpuFlags(int enable_flags);
 
 // Low level cpuid for X86. Returns zeros on other CPUs.
 // eax is the info type that you want.
 // ecx is typically the cpu number, and should normally be zero.
 LIBYUV_API
 void CpuId(uint32 eax, uint32 ecx, uint32* cpu_info);
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif
 
 #endif  // INCLUDE_LIBYUV_CPU_ID_H_  NOLINT