[Ext Registry] Do not try to re-watch registry if we are already watching it.

chrome/browser/extensions/external_registry_loader_win.cc

Index: chrome/browser/extensions/external_registry_loader_win.cc
diff --git a/chrome/browser/extensions/external_registry_loader_win.cc b/chrome/browser/extensions/external_registry_loader_win.cc
index b54835aff5923dc09df2e599efa9688b7d330261..0c1088480c2f2fc7d76b71ff0e094b469b24a53e 100644
--- a/chrome/browser/extensions/external_registry_loader_win.cc
+++ b/chrome/browser/extensions/external_registry_loader_win.cc
@@ -54,6 +54,9 @@ std::string MakePrefName(const std::string& extension_id,
 
 namespace extensions {
 
+ExternalRegistryLoader::ExternalRegistryLoader()
+    : attempted_watching_registry_(false) {}
+
 void ExternalRegistryLoader::StartLoading() {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   BrowserThread::PostTask(
@@ -200,7 +203,10 @@ void ExternalRegistryLoader::CompleteLoadAndStartWatchingRegistry() {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   LoadFinished();
 
-  // Start watching registry.
+  // Attempt to watch registry if we haven't already.
+  if (attempted_watching_registry_)
+    return;
+
   LONG result = ERROR_SUCCESS;
   if ((result = hklm_key_.Create(HKEY_LOCAL_MACHINE, kRegistryExtensions,
                                  KEY_NOTIFY | KEY_WOW64_32KEY)) ==
@@ -222,6 +228,8 @@ void ExternalRegistryLoader::CompleteLoadAndStartWatchingRegistry() {
   } else {
     LOG(WARNING) << "Error observing HKCU: " << result;
   }
+
+  attempted_watching_registry_ = true;
 }
 
 void ExternalRegistryLoader::OnRegistryKeyChanged(base::win::RegKey* key) {