Add private extension API to move the accessibility focus ring.

chrome/common/extensions/api/accessibility_private.json

 // Copyright 2014 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": "accessibilityPrivate",
     "compiler_options": {
       "implemented_in": "chrome/browser/accessibility/accessibility_extension_api.h"
     },
@@ skipping 141 matching lines @@
               { "$ref": "MenuItemDetails" },
               { "$ref": "RadioButtonDetails" },
               { "$ref": "SliderDetails" },
               { "$ref": "TabDetails" },
               { "$ref": "TextBoxDetails" },
               { "$ref": "TreeDetails" },
               { "$ref": "TreeItemDetails" }
             ]
           }
         }
+      },
+      {
+        "id": "ScreenRect",
+        "type": "object",
+        "description": "Bounding rectangle in global screen coordinates.",
+        "properties": {
+          "left": {"type": "integer", "description": "Left coordinate in global screen coordinates."},
+          "top": {"type": "integer", "description": "Top coordinate in global screen coordinates."},
+          "width": {"type": "integer", "description": "Width in pixels."},
+          "height": {"type": "integer", "description": "Height in pixels."}
+        }
       }
     ],
     "functions": [
       {
         "name": "setAccessibilityEnabled",
         "type": "function",
         "description": "Enables or disables the accessibility extension api. This must be set to true before event listeners or getFocusedControl will work.",
         "parameters": [
           {
             "type": "boolean",
@@ skipping 49 matching lines @@
             "parameters": [
               {
                 "name": "alerts",
                 "type": "array",
                 "items": { "$ref": "AlertInfo" },
                 "description": "Alerts being shown on the given tab."
               }
             ]
           }
         ]
+      },
+      {
+        "name": "setFocusRing",
+        "type": "function",
+        "description": "Set the bounds of the accessibility focus ring.",
+        "parameters": [
+          {
+            "name": "rects",
+            "type": "array",
+            "items": { "$ref": "ScreenRect" },
+            "description": "Array of rectangles to focus."

[David Tseng, 2014/09/10 22:50:28]

This sounds like there would be a focus action taken upon a page. Do we simply
want to substitute "focus" with "indicator" everywhere to reduce
confusion/overloading?

[dmazzoni, 2014/09/11 22:04:36]

I clarified the text a bit.

I think it's clearer to call it an accessibility focus ring here rather than an
active indicator. The concept of focus and a focus ring is well-understood, it
makes it easier to understand and easier to read throughout the Chrome codebase.
Inside ChromeVox we use "active indicator" because we have to carefully track
keyboard focus and that's not always the same as the active element.

Another reason is that I intend to use the same code in Chrome OS to implement
support for a "highlight focused element" accessibility feature independent of
ChromeVox.

+          }
+        ]
       }
     ],
     "events": [
       {
         "name": "onWindowOpened",
         "type": "function",
         "description": "Fired when a window is opened.",
         "parameters": [
           {
             "$ref": "AccessibilityObject",
@@ skipping 99 matching lines @@
           {
             "type": "boolean",
             "name": "makeAnnouncements",
             "description": "Whether to make introductory announcements."
           }
         ]
       }
     ]
   }
 ]