Implemented a policy for centralized setting of the --disk-cache-dir flag.

chrome/browser/profiles/profile_impl.cc

Index: chrome/browser/profiles/profile_impl.cc
diff --git a/chrome/browser/profiles/profile_impl.cc b/chrome/browser/profiles/profile_impl.cc
index c50603d52ffaf9c03737c77be5d762cf11c3e21c..c1ef62497bb1b14c45aaa5ada64e8e001feebd54 100644
--- a/chrome/browser/profiles/profile_impl.cc
+++ b/chrome/browser/profiles/profile_impl.cc
@@ -152,6 +152,12 @@ void GetCacheParameters(ContextType type, FilePath* cache_path,
     *cache_path = CommandLine::ForCurrentProcess()->GetSwitchValuePath(
         switches::kDiskCacheDir);
   }
+#if !defined(OS_CHROMEOS)
+  // And if a policy is set this should have even higher precedence.
+  PrefService* prefs = g_browser_process->local_state();
+  if (prefs && prefs->IsManagedPreference(prefs::kDiskCacheDir))
+    *cache_path = prefs->GetFilePath(prefs::kDiskCacheDir);
+#endif
 
   const char* arg = kNormalContext == type ? switches::kDiskCacheSize :
                                              switches::kMediaCacheSize;