Change JS parameter to camel case.

chrome/common/extensions/api/tabs.json

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "tabs",
     "description": "Use the <code>chrome.tabs</code> API to interact with the browser's tab system. You can use this API to create, modify, and rearrange tabs in the browser.",
     "types": [
       {
@@ skipping 61 matching lines @@
           "mode": {
             "$ref": "ZoomSettingsMode",
             "description": "Defines how zoom changes are handled, i.e. which entity is responsible for the actual scaling of the page; defaults to <code>automatic</code>.",
             "optional": true
           },
           "scope": {
             "$ref": "ZoomSettingsScope",
             "description": "Defines whether zoom changes will persist for the page's origin, or only take effect in this tab; defaults to <code>per-origin</code> when in <code>automatic</code> mode, and <code>per-tab</code> otherwise.",
             "optional": true
           },
-          "default_zoom_factor": {
+          "defaultZoomFactor": {
             "type": "number",
-            "name": "defaultZoomFactor",
             "optional": true,
             "description": "Used to return the default zoom level for the current tab in calls to tabs.getZoomSettings."
           }
         }
       },
       {
         "id": "TabStatus",
         "type": "string",
         "enum": ["loading", "complete"],
         "description": "Whether the tabs have completed loading."
@@ skipping 1013 matching lines @@
             "tabId": {"type": "integer", "minimum": 0},
             "oldZoomFactor": {"type": "number"},
             "newZoomFactor": {"type": "number"},
             "zoomSettings": {"$ref": "ZoomSettings"}
           }
         }]
       }
     ]
   }
 ]