Add file access modes to sk_exists.

src/ports/SkOSFile_win.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkOSFile.h"
 
 #include "SkTFitsIn.h"
 
 #include <io.h>
 #include <stdio.h>
 #include <sys/stat.h>
 
+bool sk_exists(const char *path, SkFILE_Flags flags) {
+    int mode = 0; // existence
+    if (flags & kRead_SkFILE_Flag) {
+        mode |= 4; // read
+    }
+    if (flags & kWrite_SkFILE_Flag) {
+        mode |= 2; // write
+    }
+    return (0 == _access(path, mode));
+}
+
 typedef struct {
     ULONGLONG fVolume;
     ULONGLONG fLsbSize;
     ULONGLONG fMsbSize;
 } SkFILEID;
 
 static bool sk_ino(SkFILE* f, SkFILEID* id) {
     int fileno = _fileno((FILE*)f);
     if (fileno < 0) {
         return false;
@@ skipping 76 matching lines @@
 }
 
 void* sk_fmmap(SkFILE* f, size_t* length) {
     int fileno = sk_fileno(f);
     if (fileno < 0) {
         return NULL;
     }
 
     return sk_fdmmap(fileno, length);
 }