Refactor GlobalShortcutListener.

chrome/browser/extensions/extension_commands_global_registry.cc

Index: chrome/browser/extensions/extension_commands_global_registry.cc
diff --git a/chrome/browser/extensions/extension_commands_global_registry.cc b/chrome/browser/extensions/extension_commands_global_registry.cc
index aa11b9c5c5cf667de5a315d7573ae6d1bb1fc478..541e82db271dfe693d6a0125b62072e92aa86e79 100644
--- a/chrome/browser/extensions/extension_commands_global_registry.cc
+++ b/chrome/browser/extensions/extension_commands_global_registry.cc
@@ -78,13 +78,19 @@ void ExtensionCommandsGlobalRegistry::AddExtensionKeybinding(
 
     event_targets_[iter->second.accelerator()].push_back(
         std::make_pair(extension->id(), iter->second.command_name()));
-    // Shortcuts except media keys have only one target in the list. See comment
-    // about |event_targets_|.
-    if (!extensions::CommandService::IsMediaKey(iter->second.accelerator()))
+    if (!extensions::CommandService::IsMediaKey(iter->second.accelerator())) {
+      // Shortcuts except media keys have only one target in the list. See
+      // comment about |event_targets_|.
       DCHECK(event_targets_[iter->second.accelerator()].size() == 1);
+    } else if (event_targets_[iter->second.accelerator()].size() > 1) {
+      // Now the |iter->second.accelerator()| is one of the media keys, we have
+      // registerd it successfully, so pass it by.
+      continue;
+    }
 
-    GlobalShortcutListener::GetInstance()->RegisterAccelerator(
-      iter->second.accelerator(), this);
+    if (!GlobalShortcutListener::GetInstance()->RegisterAccelerator(
+            iter->second.accelerator(), this))

[zhchbin, 2013/12/17 13:34:32]

You may ask why I didn't call RegisterAccelerator early, before the |push_back|.
Think about multiply media keys.

[Finnur, 2013/12/17 14:31:40]

Wondering if this would be simpler (you'll need to remove lines 79-80) (and this
is pseudo, haven't compiled it)...

size_t target_count =
    event_targets_.find(iter->second.accelerator()) != event_targets_.end() ?
        event_targets_[iter->second.accelerator()].size() : 0;

if (extensions::CommandService::IsMediaKey(iter->second.accelerator()) &&
    target_count > 0U)
  continue;  // Shortcut listener already listening for this media key.
}

DCHECK_EQ(0U, target_count);
if (GlobalShortcutListener::GetInstance()->RegisterAccelerator(
    iter->second.accelerator(), this)) {
  event_targets_[iter->second.accelerator()].push_back(
      std::make_pair(extension->id(), iter->second.command_name()));
}

[zhchbin, 2013/12/17 15:15:46]

Thanks very much!

In this case we should also push a pair (extension id, command name) to the
event_targets. Otherwise the test case
"GlobalCommandsApiTest.GlobalDuplicatedMediaKey" will fail. 

Done with also adding a pair.

+      event_targets_.erase(iter->second.accelerator());
   }
 }