Add Google Docs as a default app

chrome/browser/resources/default_apps/external_extensions.json

 // Dictionary of default apps to install into new profiles.  Each entry maps
 // the extension's id to its crx's path (relative to this file) and the version
 // of the extension contained in the crx.
 //
 // When an extension is added or removed here, the two lists 'default_apps_list'
 // and 'default_apps_list_linux_dest' in build/common.gypi must also be updated.
 {
   "blpcfgokakmgnkcojhhkbfbldkacnbeo" : {
     "external_crx": "youtube.crx",
     "external_version": "4.2.5",
     "is_bookmark_app": true
   },
   "coobgpohoikkiipiblmjeljniedjpjpf" : {
     "external_crx": "search.crx",
     "external_version": "0.0.0.19",
     "is_bookmark_app": true
   },
   "pjkljhegncpnkpknbcohdijeoejaedia" : {
     "external_crx": "gmail.crx",
     "external_version": "7"
+  },
+  "apdfllckaahabafndbhieahigkjlhalf" : {
+    "external_crx": "docs.crx",
+    "external_version": "5.4"
   }
 }