chrome: remove --disable-async-dns switch

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 29c162d1f303c74e5232353b879cb586c28a9093..709201b97c1d4f5c4d96c7bf98c1b3ae5fdae5d5 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -173,9 +173,6 @@ const char kDisableAboutInSettings[]        = "disable-about-in-settings";
 // app to their shelf (or platform-specific equivalent)
 const char kDisableAddToShelf[] = "disable-add-to-shelf";
 
-// Disables the experimental asynchronous DNS client.
-const char kDisableAsyncDns[]               = "disable-async-dns";
-
 // Disable several subsystems which run network requests in the background.
 // This is for use when doing network performance testing to avoid noise in the
 // measurements.