[Windows] Finish global and non-global media keys support on Windows.

chrome/browser/extensions/global_shortcut_listener_x11.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/global_shortcut_listener_x11.h"
 
 #include "base/x11/x11_error_tracker.h"
 #include "content/public/browser/browser_thread.h"
 #include "ui/base/accelerators/accelerator.h"
 #include "ui/events/keycodes/keyboard_code_conversion_x.h"
@@ skipping 92 matching lines @@
 bool GlobalShortcutListenerX11::Dispatch(const base::NativeEvent& event) {
   if (event->type == KeyPress)
     OnXKeyPressEvent(event);
 
   return true;
 }
 
 void GlobalShortcutListenerX11::RegisterAccelerator(
     const ui::Accelerator& accelerator,
     GlobalShortcutListener::Observer* observer) {
+  if (registered_hot_keys_.find(accelerator) != registered_hot_keys_.end()) {
+    // The shortcut has already been registered. Some shortcuts, such as
+    // MediaKeys can have multiple targets, all keyed off of the same
+    // accelerator.
+    return;
+  }
+
   int modifiers = GetNativeModifiers(accelerator);
   KeyCode keycode = XKeysymToKeycode(x_display_, accelerator.key_code());
   base::X11ErrorTracker err_tracker;
 
   // Because XGrabKey only works on the exact modifiers mask, we should register
   // our hot keys with modifiers that we want to ignore, including Num lock,
   // Caps lock, Scroll lock. See comment about |kModifiersMasks|.
   for (size_t i = 0; i < arraysize(kModifiersMasks); ++i) {
     XGrabKey(x_display_, keycode, modifiers | kModifiersMasks[i],
              x_root_window_, False, GrabModeAsync, GrabModeAsync);
@@ skipping 49 matching lines @@
   modifiers |= (x_event->xkey.state & ControlMask) ? ui::EF_CONTROL_DOWN : 0;
   modifiers |= (x_event->xkey.state & Mod1Mask) ? ui::EF_ALT_DOWN : 0;
 
   ui::Accelerator accelerator(
       ui::KeyboardCodeFromXKeyEvent(x_event), modifiers);
   if (registered_hot_keys_.find(accelerator) != registered_hot_keys_.end())
     instance.Get().NotifyKeyPressed(accelerator);
 }
 
 }  // namespace extensions