Make Windows accessibility event firing aware of guest / child frames.

content/browser/accessibility/browser_accessibility_cocoa.mm

Index: content/browser/accessibility/browser_accessibility_cocoa.mm
diff --git a/content/browser/accessibility/browser_accessibility_cocoa.mm b/content/browser/accessibility/browser_accessibility_cocoa.mm
index 7668c851f55fb7f6fd06939e0beca6e63949eda9..cbc46f9d14e11ff7462ebdd877df55bdae7dee67 100644
--- a/content/browser/accessibility/browser_accessibility_cocoa.mm
+++ b/content/browser/accessibility/browser_accessibility_cocoa.mm
@@ -517,16 +517,14 @@ NSDictionary* attributeToMethodNameMap = nil;
 
   // Get the delegate for the topmost BrowserAccessibilityManager, because
   // that's the only one that can convert points to their origin in the screen.
-  BrowserAccessibilityManager* manager = browserAccessibility_->manager();
-  BrowserAccessibility* root = manager->GetRoot();
-  while (root->GetParent())
-    root = root->GetParent()->manager()->GetRoot();
-  manager = root->manager();
-  BrowserAccessibilityDelegate* delegate = manager->delegate();
-
-  gfx::Rect bounds(origin.x, origin.y, size.width, size.height);
-  gfx::Point point = delegate->AccessibilityOriginInScreen(bounds);
-  return NSMakePoint(point.x(), point.y());
+  BrowserAccessibilityDelegate* delegate = GetDelegateFromRootManager();
+  if (delegate) {
+    gfx::Rect bounds(origin.x, origin.y, size.width, size.height);
+    gfx::Point point = delegate->AccessibilityOriginInScreen(bounds);
+    return NSMakePoint(point.x(), point.y());
+  } else {
+    return NSZeroPoint;
+  }
 }
 
 // Returns a string indicating the NSAccessibility role of this object.
@@ -1548,4 +1546,3 @@ NSDictionary* attributeToMethodNameMap = nil;
 }
 
 @end
-