Parse createUrl field of apps.list Drive API.

chrome/test/data/drive/applist.json

 {
  "kind": "drive#appList",
  "etag": "\"Jm4BaSnCWNND-noZsHINRqj4ABC/tuqRBw0lvjUdPtc_2msA1tN4XYZ\"",
  "selfLink": "https://www.googleapis.com/drive/v2/apps",
  "items": [
   {
    "kind": "drive#app",
    "id": "123456788192",
    "name": "Drive app 1",
    "objectType": "",
    "supportsCreate": true,
    "supportsImport": true,
    "installed": true,
    "authorized": false,
    "productUrl": "https://chrome.google.com/webstore/detail/abcdefghabcdefghabcdefghabcdefgh",
+   "createUrl": "https://www.example.com/createForApp1",
    "primaryMimeTypes": [
     "application/vnd.google-apps.drive-sdk.123456788192"
    ],
    "secondaryMimeTypes": [
     "text/html",
     "text/plain"
    ],
    "primaryFileExtensions": [
     "exe",
     "com"
@@ skipping 34 matching lines @@
   {
    "kind": "drive#app",
    "id": "876543210000",
    "name": "Drive app 2",
    "objectType": "",
    "supportsCreate": false,
    "supportsImport": false,
    "installed": true,
    "authorized": false,
    "productUrl": "https://chrome.google.com/webstore/detail/hgfedcbahgfedcbahgfedcbahgfedcba",
+   "createUrl": "https://www.example.com/createForApp2",
    "primaryMimeTypes": [
     "image/jpeg",
     "image/png",
     "application/vnd.google-apps.drive-sdk.876543210000"
    ],
    "icons": [
     {
      "category": "application",
      "size": 10,
      "iconUrl": "http://www.example.com/10.png"
     },
     {
      "category": "document",
      "size": 10,
      "iconUrl": "http://www.example.com/d10.png"
     },
     {
      "category": "documentShared",
      "size": 10,
      "iconUrl": "http://www.example.com/ds10.png"
     }
    ]
   }
  ]
 }