Add support for retrieving image thumbnails as part of the accessibility tree.

chrome/common/extensions/api/automation_internal.idl

 // 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.
 
 // This is the implementation layer of the chrome.automation API, and is
 // essentially a translation of the internal accessibility tree update system
 // into an extension API.
 namespace automationInternal {
   // Data for an accessibility event and/or an atomic change to an accessibility
   // tree. See ui/accessibility/ax_tree_update.h for an extended explanation of
@@ skipping 13 matching lines @@
 
     // The mouse coordinates when this event fired.
     double mouseX;
     double mouseY;
   };
 
   // All possible actions that can be performed on automation nodes.
   enum ActionType {
     focus,
     doDefault,
+    getImageData,
     makeVisible,
     setAccessibilityFocus,
     setSequentialFocusNavigationStartingPoint,
     setSelection,
     showContextMenu
   };
 
   // Arguments required for all actions supplied to performAction.
   dictionary PerformActionRequiredParams {
     long treeID;
@@ skipping 16 matching lines @@
     long automationNodeID;
     DOMString selector;
   };
 
   // Arguments for the enableTab function.
   dictionary EnableTabParams {
     long routingID;
     long? tabID;
   };
 
+  // Arguments for the getImageData function.
+  dictionary GetImageDataParams {
+    long maxWidth;
+    long maxHeight;
+  };
+
   // Returns the accessibility tree id of the web contents who's accessibility
   // was enabled using enableTab().
   callback EnableTabCallback = void(long tree_id);
 
   // Callback called when enableDesktop() returns.
   callback EnableDesktopCallback = void();
 
   // Callback called when querySelector() returns.
   callback QuerySelectorCallback = void(long resultAutomationNodeID);
 
@@ skipping 29 matching lines @@
     static void onTreeChange(long observerID,
                              long treeID,
                              long nodeID,
                              DOMString changeType);
 
     static void onChildTreeID(long treeID, long nodeID);
 
     static void onNodesRemoved(long treeID, long[] nodeIDs);
   };
 };