Implement path canonicalization on Windows to fix infinite loop on cyclic includes.

runtime/bin/file_win.cc

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <fcntl.h>
 #include <io.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
 
@@ skipping 103 matching lines @@
 bool File::IsAbsolutePath(const char* pathname) {
   // Should we consider network paths?
   if (pathname == NULL) return false;
   return (strlen(pathname) > 2) &&
       (pathname[1] == ':') &&
       (pathname[2] == '\\');
 }
 
 
 char* File::GetCanonicalPath(const char* pathname) {
-  // TODO(176): Need to implement this.
-  return strdup(pathname);
+  int required_size = GetFullPathName(pathname, 0, NULL, NULL);
+  char* path = static_cast<char*>(malloc(required_size));
+  int written = GetFullPathName(pathname, required_size, path, NULL);
+  ASSERT(written == (required_size - 1));
+  return path;
 }
 
 
 const char* File::PathSeparator() {
   return "\\";
 }
 
 
 const char* File::StringEscapedPathSeparator() {
   return "\\\\";
 }