Add setSelection function to automation API.

chrome/renderer/resources/extensions/automation_custom_bindings.js

Index: chrome/renderer/resources/extensions/automation_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/automation_custom_bindings.js b/chrome/renderer/resources/extensions/automation_custom_bindings.js
index ae84e27949fd3baaca5a8ab0f0819b402a5ebc7e..508951610a5afbca8f1b6457f60e599dd9fc3038 100644
--- a/chrome/renderer/resources/extensions/automation_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/automation_custom_bindings.js
@@ -127,6 +127,23 @@ automation.registerCustomHook(function(bindingsAPI) {
     addTreeChangeObserver(observer);
   });
 
+  apiFunctions.setHandleRequest('setDocumentSelection', function(params) {
+    var anchorNodeImpl = privates(params.anchorObject).impl;
+    var focusNodeImpl = privates(params.focusObject).impl;
+    if (anchorNodeImpl.treeID !== focusNodeImpl.treeID)
+      throw new Error('Selection anchor and focus must be in the same tree.');
+    if (anchorNodeImpl.treeID === DESKTOP_TREE_ID) {
+      throw new Error('Use AutomationNode.setSelection to set the selection ' +
+          'in the desktop tree.');
+    }
+    automationInternal.performAction({ treeID: anchorNodeImpl.treeID,
+                                       automationNodeID: anchorNodeImpl.id,
+                                       actionType: 'setSelection'},
+                                     { focusNodeID: focusNodeImpl.id,
+                                       anchorOffset: params.anchorOffset,
+                                       focusOffset: params.focusOffset });
+  });
+
 });
 
 automationInternal.onTreeChange.addListener(function(treeID,