Add support for omnibox.onInputStarted and onInputCancelled.

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 1328 matching lines @@
                 "description": "The html file to show in a popup.  If set to the empty string (''), no popup is shown."
               }
             }
           }
         ]
       }
     ],
     "events": [
       {
         "name": "onClicked",
+        "perExtensionEvent": true,
         "type": "function",
         "description": "Fired when a page action icon is clicked.  This event will not fire if the page action has a popup.",
         "parameters": [
           {
             "name": "tab",
             "$ref": "Tab"
           }
         ]
       }
     ]
@@ skipping 127 matching lines @@
                 "description": "Limits the change to when a particular tab is selected. Automatically resets when the tab is closed."
               }
             }
           }
         ]
       }
     ],
     "events": [
       {
         "name": "onClicked",
+        "perExtensionEvent": true,
         "type": "function",
         "description": "Fired when a browser action icon is clicked.  This event will not fire if the browser action has a popup.",
         "parameters": [
           {
             "name": "tab",
             "$ref": "Tab"
           }
         ]
       }
     ]
@@ skipping 1619 matching lines @@
       },
       {
         "name": "styleDim",
         "type": "function",
         "description": "Constructor for the descriptionStyles parameter of the suggest callback. This style designates a region of dim helper text.",
         "parameters": [ {"type": "integer", "name": "offset", "minimum": 0} ]
       }
     ],
     "events": [
       {
+        "name": "onInputStarted",
+        "perExtensionEvent": true,
+        "type": "function",
+        "description": "User has started a keyword input session by typing the extension's keyword. This is guaranteed to be sent exactly once per input session, and before any onInputChanged events.",
+        "parameters": []
+      },
+      {
         "name": "onInputChanged",
+        "perExtensionEvent": true,
         "type": "function",
         "description": "User has changed what is typed into the omnibox.",
         "parameters": [
           {
             "type": "string",
             "name": "text"
           },
           {
             "name": "suggest",
             "type": "function",
             "description": "A callback passed to the onInputChanged event used for sending suggestions back to the browser.",
             "parameters": [
               {"type": "integer", "name": "requestId"},
               {
                 "type": "array",
                 "description": "Array of suggest results",
                 "items": {
                   "$ref": "SuggestResult"
                 }
               }
             ]
           }
         ]
       },
       {
         "name": "onInputEntered",
+        "perExtensionEvent": true,
         "type": "function",
         "description": "User has accepted what is typed into the omnibox.",
         "parameters": [
           {
             "type": "string",
             "name": "text"
           }
         ]
+      },
+      {
+        "name": "onInputCancelled",
+        "perExtensionEvent": true,
+        "type": "function",
+        "description": "User has ended the keyword input session without accepting the input.",
+        "parameters": []
       }
     ]
   }
 ]