Update PDF accessibility when zoom level changes

content/renderer/accessibility/render_accessibility_impl.cc

Index: content/renderer/accessibility/render_accessibility_impl.cc
diff --git a/content/renderer/accessibility/render_accessibility_impl.cc b/content/renderer/accessibility/render_accessibility_impl.cc
index de8c4e877fc57a99631c6ed4d22e149a63aaa690..410342bb7edc23000dd3733d26ed2a14e82fdfec 100644
--- a/content/renderer/accessibility/render_accessibility_impl.cc
+++ b/content/renderer/accessibility/render_accessibility_impl.cc
@@ -259,6 +259,14 @@ void RenderAccessibilityImpl::SetPdfTreeSource(
   pdf_tree_source_ = pdf_tree_source;
   pdf_serializer_.reset(new PdfAXTreeSerializer(pdf_tree_source_));
 
+  OnPdfRootNodeUpdated();
+}
+
+void RenderAccessibilityImpl::OnPdfRootNodeUpdated() {
+  // Search the accessibility tree for an EMBED element and post a
+  // children changed notification on it to force it to update the
+  // PDF accessibility tree.
+
   ScopedFreezeBlinkAXTreeSource freeze(&tree_source_);
   WebAXObject root = tree_source_.GetRoot();
   if (!root.updateLayoutAndCheckValidity())