Log the error result when observing a registry key fails.

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 3241d4934db3bf2d494d3395e7a1fc62d40f8fed..b54835aff5923dc09df2e599efa9688b7d330261 100644
--- a/chrome/browser/extensions/external_registry_loader_win.cc
+++ b/chrome/browser/extensions/external_registry_loader_win.cc
@@ -201,24 +201,26 @@ void ExternalRegistryLoader::CompleteLoadAndStartWatchingRegistry() {
   LoadFinished();
 
   // Start watching registry.
-  if (hklm_key_.Create(HKEY_LOCAL_MACHINE, kRegistryExtensions,
-                       KEY_NOTIFY | KEY_WOW64_32KEY) == ERROR_SUCCESS) {
+  LONG result = ERROR_SUCCESS;
+  if ((result = hklm_key_.Create(HKEY_LOCAL_MACHINE, kRegistryExtensions,
+                                 KEY_NOTIFY | KEY_WOW64_32KEY)) ==
+      ERROR_SUCCESS) {
     base::win::RegKey::ChangeCallback callback =
         base::Bind(&ExternalRegistryLoader::OnRegistryKeyChanged,
                    base::Unretained(this), base::Unretained(&hklm_key_));
     hklm_key_.StartWatching(callback);
   } else {
-    LOG(WARNING) << "Error observing HKLM.";
+    LOG(WARNING) << "Error observing HKLM: " << result;

[lazyboy, 2017/02/15 00:19:56]

Maybe we should remove logging this and keep only the HKCU warning below?

[Wez, 2017/02/15 00:33:21]

Actually it seems like a legitimate error; IIUC correctly the intention of this
code is simply to watch and read from the key(s), so I think we should probably
fix the call-site to try to open the key just for reading.

WDYT?

   }
 
-  if (hkcu_key_.Create(HKEY_CURRENT_USER, kRegistryExtensions, KEY_NOTIFY) ==
-      ERROR_SUCCESS) {
+  if ((result = hkcu_key_.Create(HKEY_CURRENT_USER, kRegistryExtensions,
+                                 KEY_NOTIFY)) == ERROR_SUCCESS) {
     base::win::RegKey::ChangeCallback callback =
         base::Bind(&ExternalRegistryLoader::OnRegistryKeyChanged,
                    base::Unretained(this), base::Unretained(&hkcu_key_));
     hkcu_key_.StartWatching(callback);
   } else {
-    LOG(WARNING) << "Error observing HKCU.";
+    LOG(WARNING) << "Error observing HKCU: " << result;
   }
 }