Don't create a BrowserAccessibilityManager for a child frame on Android.

content/browser/renderer_host/render_widget_host_view_android.cc

Index: content/browser/renderer_host/render_widget_host_view_android.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_android.cc b/content/browser/renderer_host/render_widget_host_view_android.cc
index e7336e28507d7b642b2e5d92abf23f454822a89b..db406b611255e8a312adc574069adfe35cdd1e5c 100644
--- a/content/browser/renderer_host/render_widget_host_view_android.cc
+++ b/content/browser/renderer_host/render_widget_host_view_android.cc
@@ -1425,6 +1425,16 @@ void RenderWidgetHostViewAndroid::OnSetNeedsFlushInput() {
 BrowserAccessibilityManager*
     RenderWidgetHostViewAndroid::CreateBrowserAccessibilityManager(
         BrowserAccessibilityDelegate* delegate) {
+  // TODO(dmazzoni): Currently there can only be one
+  // BrowserAccessibilityManager per ContentViewCore, so return NULL
+  // if there's already a BrowserAccessibilityManager for the main
+  // frame.  Eventually, in order to support cross-process iframes on
+  // Android we'll need to add support for a
+  // BrowserAccessibilityManager for a child frame.
+  // http://crbug.com/423846
+  if (!host_ || host_->GetRootBrowserAccessibilityManager())
+    return NULL;
+
   base::android::ScopedJavaLocalRef<jobject> obj;
   if (content_view_core_)
     obj = content_view_core_->GetJavaObject();