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

chrome/test/data/extensions/api_test/keybinding/non_global_media_keys_0/manifest.json

+{
+  "name": "An extension to test non-global media keys command",
+  "version": "1.0",
+  "manifest_version": 2,
+  "background": {
+    "scripts": ["background.js"]
+  },
+  "commands": {
+    "MediaStop-non-global-0": {
+      "suggested_key": {
+        "default": "MediaStop"
+      },
+      "description": "Test passes if called."
+    },
+    "MediaStop-non-global-1": {
+      "suggested_key": {
+        "default": "MediaStop"

[Finnur, 2013/11/12 16:27:54]

Hmmm... An extension can register for the same shortcut twice. I don't think
that would be useful for extension developers and is likely to be the result of
an error (e.g. copy paste). I would actually enforce one command per shortcut by
throwing an error (and test for it).

[zhchbin, 2013/11/13 05:01:57]

Since I have changed the key by appending extension id (instead of my stupid
counter) when adding media key binding preference, so now it's one command per
shortcut when installing an extension. I would try to add this rule when parsing
commands from manifest.

+      },
+      "description": "Test passes if called."
+    },
+    "MediaNextTrack-non-global": {
+      "suggested_key": {
+        "default": "MediaNextTrack"
+      },
+      "description": "Test failed if called (We didn't active this key)."
+    }
+  }
+}