Rearrange the input APIs into more suitable groupings.

chrome/test/data/extensions/api_test/input_ime/background.html

 <script>
   function setMenuItemsTest() {
-    chrome.experimental.input.setMenuItems({
+    chrome.experimental.input.ime.setMenuItems({
       "engineID": "test",
       "items": [{
         "id": "Menu 1",
         "label": "Menu 1",
         "style": "check",
         "visible": true,
         "enabled": true
       }, {
         "id": "Menu 2",
         "label": "Menu 2",
         "style": "radio",
         "visible": true,
         "enabled": true
       }]
     }, function () {
       chrome.test.assertNoLastError();
       chrome.test.succeed();
     });
   }
 
   function updateMenuItemsTest() {
-    chrome.experimental.input.updateMenuItems({
+    chrome.experimental.input.ime.updateMenuItems({
       "engineID": "test",
       "items": [{
         "id": "Menu 1",
         "enabled": false
       }, {
         "id": "Menu 2",
         "visible": false,
       }]
     }, function () {
       chrome.test.assertNoLastError();
       chrome.test.succeed();
     });
   }
 
   chrome.test.runTests([setMenuItemsTest, updateMenuItemsTest]);
 </script>