Enable DumpAccessibilityTree tests to use cross-process iframes.

content/browser/accessibility/browser_accessibility_manager.cc

Index: content/browser/accessibility/browser_accessibility_manager.cc
diff --git a/content/browser/accessibility/browser_accessibility_manager.cc b/content/browser/accessibility/browser_accessibility_manager.cc
index f56b84851dc0ce48bd5edb417bd96b5d5d1eaa3b..d82dd42aada99b58b465dabbfcc0759e61f0b39e 100644
--- a/content/browser/accessibility/browser_accessibility_manager.cc
+++ b/content/browser/accessibility/browser_accessibility_manager.cc
@@ -615,16 +615,23 @@ void BrowserAccessibilityManager::OnAtomicUpdateFinished(
   }
 }
 
-BrowserAccessibilityDelegate*
-    BrowserAccessibilityManager::GetDelegateFromRootManager() {
+BrowserAccessibilityManager* BrowserAccessibilityManager::GetRootManager() {
   if (!GetRoot())

[David Tseng, 2016/01/07 00:02:29]

When does this happen?

[dmazzoni, 2016/01/07 19:19:08]

In the middle of a tree update when we call something like OnNodeWillBeDeleted.
I've thought about rewriting that so that it precomputes the nodes that would be
deleted so it doesn't ever have to call back when the tree is broken.

     return nullptr;
   int parent_tree_id = GetTreeData().parent_tree_id;
   BrowserAccessibilityManager* parent_manager =
       BrowserAccessibilityManager::FromID(parent_tree_id);
   if (parent_manager)
-    return parent_manager->GetDelegateFromRootManager();
-  return delegate();
+    return parent_manager->GetRootManager();
+  return this;
+}
+
+BrowserAccessibilityDelegate*
+    BrowserAccessibilityManager::GetDelegateFromRootManager() {
+  BrowserAccessibilityManager* root_manager = GetRootManager();
+  if (root_manager)
+    return root_manager->delegate();
+  return nullptr;
 }
 
 ui::AXTreeUpdate