fix warning on visual C for mips cpu detect

source/cpu_id.cc

 /*
  *  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 146 matching lines @@
       }
     }
   }
   fclose(f);
   return 0;
 }
 
 LIBYUV_API SAFEBUFFERS
 int MipsCpuCaps(const char* cpuinfo_name, const char ase[]) {
   char cpuinfo_line[512];
-  int len = strlen(ase);
+  int len = (int)strlen(ase);
   FILE* f = fopen(cpuinfo_name, "r");
   if (!f) {
     // ase enabled if /proc/cpuinfo is unavailable.
-    if(strcmp(ase, " msa") == 0) {
+    if (strcmp(ase, " msa") == 0) {
       return kCpuHasMSA;
     }
-    if(strcmp(ase, " dspr2") == 0) {
+    if (strcmp(ase, " dspr2") == 0) {
       return kCpuHasDSPR2;
     }
   }
   while (fgets(cpuinfo_line, sizeof(cpuinfo_line) - 1, f)) {
     if (memcmp(cpuinfo_line, "ASEs implemented", 16) == 0) {
       char* p = strstr(cpuinfo_line, ase);
       if (p && (p[len] == ' ' || p[len] == '\n')) {
         fclose(f);
-        if(strcmp(ase, " msa") == 0) {
+        if (strcmp(ase, " msa") == 0) {
           return kCpuHasMSA;
         }
-        if(strcmp(ase, " dspr2") == 0) {
+        if (strcmp(ase, " dspr2") == 0) {
           return kCpuHasDSPR2;
         }
       }
     }
   }
   fclose(f);
   return 0;
 }
 
 // CPU detect function for SIMD instruction sets.
@@ skipping 132 matching lines @@
 // Note that use of this function is not thread safe.
 LIBYUV_API
 void MaskCpuFlags(int enable_flags) {
   cpu_info_ = InitCpuFlags() & enable_flags;
 }
 
 #ifdef __cplusplus
 }  // extern "C"
 }  // namespace libyuv
 #endif