Fix three Windows base_unittests to not require admin

These three base_unittests tests fail when run as non-admin on Windows
if %temp% is set to a non-standard location such as d:\src\temp:

- FileTest.GetInfoForDirectory
- FileUtilTest.FileEnumeratorTest
- FileUtilTest.NormalizeFilePathReparsePoints

They all fail because the default user doesn't have enough permissions
to open the directories with FILE_ALL_ACCESS.

Asking for fewer permissions allows the tests to pass regardless of
user-type and %temp% location.

R=rvargas@chromium.org
BUG=533018

Review URL: https://codereview.chromium.org/1348533003

Cr-Commit-Position: refs/heads/master@{#349485}

base/files/file_unittest.cc

@@ -495,7 +495,7 @@ TEST(FileTest, GetInfoForDirectory) {
 
   base::File dir(
       ::CreateFile(empty_dir.value().c_str(),
-                   FILE_ALL_ACCESS,
+                   GENERIC_READ | GENERIC_WRITE,
                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
                    NULL,
                    OPEN_EXISTING,

base/files/file_util_unittest.cc

@@ -134,7 +134,7 @@ class ReparsePoint {
   ReparsePoint(const FilePath& source, const FilePath& target) {
     dir_.Set(
       ::CreateFile(source.value().c_str(),
-                   FILE_ALL_ACCESS,
+                   GENERIC_READ | GENERIC_WRITE,
                    FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
                    NULL,
                    OPEN_EXISTING,