Add chrome.inputMethodPrivate.onImeMenuActivationChanged API.

chrome/common/extensions/api/input_method_private.json

Index: chrome/common/extensions/api/input_method_private.json
diff --git a/chrome/common/extensions/api/input_method_private.json b/chrome/common/extensions/api/input_method_private.json
index 5fe854708bda0c7f760a5c4478bde2be7db6b6a1..3dc76ee94209b012ac6c8fb162bb64b3c554585e 100644
--- a/chrome/common/extensions/api/input_method_private.json
+++ b/chrome/common/extensions/api/input_method_private.json
@@ -225,6 +225,17 @@
             }
           }
         ]
+      }, {
+        "name": "onImeMenuActivationChanged",
+        "type": "function",
+        "description": "Fired when the system IME Menu is activated",

[Devlin, 2016/01/13 18:11:27]

nit: lowercase "menu"
Is this only fired when the menu is activated?  Or also when it is deactivated? 
(I think the latter, in which case this should say "Fired when the system IME
menu is activated or deactivated.")

[Azure Wei, 2016/01/14 09:38:26]

Done.

+        "parameters": [
+          {
+            "name": "activation",
+            "type": "boolean",
+            "description": "Whether the IME menu is activated or deactivated"

[Devlin, 2016/01/13 18:11:27]

nit: the phrasing here is a bit weird, because it makes it difficult to
understand whether this refers to the current state, or the state it was
transitioned out of.  Assuming it's the current state, say something like
"Whether the IME menu is currently active."

[Azure Wei, 2016/01/14 09:38:26]

Done.

+          }
+        ]
       }
     ]
   }