Simple Cache: stop running index file tests on Windows

net/disk_cache/entry_unittest.cc

Index: net/disk_cache/entry_unittest.cc
diff --git a/net/disk_cache/entry_unittest.cc b/net/disk_cache/entry_unittest.cc
index 188a589fa055fa2d3783675c4184893db8cbe9c0..8d4161bd18d9556a777889c14de6e055d7c15d89 100644
--- a/net/disk_cache/entry_unittest.cc
+++ b/net/disk_cache/entry_unittest.cc
@@ -2297,8 +2297,9 @@ TEST_F(DiskCacheEntryTest, KeySanityCheck) {
   DisableIntegrityCheck();
 }
 
-// The simple cache backend isn't intended to work on Windows, which has very
-// different file system guarantees from Linux.
+// The Simple Cache backend requires a few guarantees from the filesystem like
+// atomic renaming of recently open files. Those guarantees are not provided in
+// general on Windows.
 #if defined(OS_POSIX)
 
 TEST_F(DiskCacheEntryTest, SimpleCacheInternalAsyncIO) {