Lands http://codereview.chromium.org/3153008 for bryeung:

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 2182 matching lines @@
         ],
         "returns": {
           "type": "string",
           "description": "Message localized for current locale."
         }
       }
     ],
     "events": []
   },
   {
+    "namespace": "experimental.input",
+    "nodoc": true,
+    "types": [],
+    "functions": [
+      {
+        "name": "sendKeyboardEvent",
+        "type": "function",
+        "description": "Send a keyboard event to Chrome.",
+        "parameters": [
+          { "type": "object",
+            "name": "event",
+            "properties": {
+              "type": {
+                "type": "string",
+                "description": "One of 'keyup' or 'keydown'."
+              },
+              "keyIdentifier": {
+                "type": "string",
+                "description": "See http://www.w3.org/TR/2003/NOTE-DOM-Level-3-Events-20031107/keyset.html#KeySet-Set"
+              },
+              "altKey": {
+                "type": "boolean",
+                "optional": true,
+                "description": "Whether or not the ALT key is pressed."
+              },
+              "ctrlKey": {
+                "type": "boolean",
+                "optional": true,
+                "description": "Whether or not the CTRL key is pressed."
+              },
+              "metaKey": {
+                "type": "boolean",
+                "optional": true,
+                "description": "Whether or not the META key is pressed."
+              },
+              "shiftKey": {
+                "type": "boolean",
+                "optional": true,
+                "description": "Whether or not the SHIFT key is pressed."
+              }
+            },
+            "description": "The keyboard event to be sent."
+          },
+          { "type": "function",
+            "name": "callback",
+            "optional": true,
+            "description": "This function is called when the event processing is completed.",
+            "parameters": []
+          }
+        ]
+      }
+    ],
+    "events": []
+  },
+  {
     "namespace": "experimental.popup",
     "nodoc": true,
     "types": [],
     "functions": [
       {
         "name": "show",
         "type": "function",
         "description": "Displays a pop-up window hosting an extension view.",
         "parameters": [
           {
@@ skipping 1628 matching lines @@
       {
         "name": "onInputCancelled",
         "perExtensionEvent": true,
         "type": "function",
         "description": "User has ended the keyword input session without accepting the input.",
         "parameters": []
       }
     ]
   }
 ]