Enable PDF accessibility when RenderFrame's accessibility mode changes.

components/pdf/renderer/pdf_accessibility_tree.cc

Index: components/pdf/renderer/pdf_accessibility_tree.cc
diff --git a/components/pdf/renderer/pdf_accessibility_tree.cc b/components/pdf/renderer/pdf_accessibility_tree.cc
index 747b932eefffb701959cae880b44d7c3c0ac2304..2f058715e9484c3f63f6408ba7de12dce8e50168 100644
--- a/components/pdf/renderer/pdf_accessibility_tree.cc
+++ b/components/pdf/renderer/pdf_accessibility_tree.cc
@@ -44,10 +44,7 @@ gfx::RectF ToGfxRectF(const PP_FloatRect& r) {
 PdfAccessibilityTree::PdfAccessibilityTree(
     content::RenderView* render_view)
     : render_view_(render_view),
-      render_accessibility_(nullptr),
       zoom_(1.0) {
-  content::RenderFrame* render_frame = render_view->GetMainRenderFrame();
-  render_accessibility_ = render_frame->GetRenderAccessibility();
 }
 
 PdfAccessibilityTree::~PdfAccessibilityTree() {
@@ -73,6 +70,12 @@ void PdfAccessibilityTree::SetAccessibilityPageInfo(
     const PP_PrivateAccessibilityPageInfo& page_info,
     const std::vector<PP_PrivateAccessibilityTextRunInfo>& text_runs,
     const std::vector<PP_PrivateAccessibilityCharInfo>& chars) {
+  content::RenderFrame* render_frame = render_view_->GetMainRenderFrame();
+  content::RenderAccessibility* render_accessibility =
+      render_frame->GetRenderAccessibility();
+  if (!render_accessibility)
+    return;
+
   uint32_t page_index = page_info.page_index;
   CHECK_GE(page_index, 0U);
   CHECK_LT(page_index, doc_info_.page_count);
@@ -171,7 +174,11 @@ void PdfAccessibilityTree::Finish() {
     update.nodes.push_back(*node);
 
   CHECK(tree_.Unserialize(update)) << update.ToString() << tree_.error();
-  render_accessibility_->SetPdfTreeSource(this);
+  content::RenderFrame* render_frame = render_view_->GetMainRenderFrame();
+  content::RenderAccessibility* render_accessibility =
+      render_frame->GetRenderAccessibility();
+  if (render_accessibility)
+    render_accessibility->SetPdfTreeSource(this);
 }
 
 void PdfAccessibilityTree::ComputeParagraphAndHeadingThresholds(
@@ -245,8 +252,12 @@ gfx::RectF PdfAccessibilityTree::ToRectF(const PP_Rect& r) {
 }
 
 ui::AXNodeData* PdfAccessibilityTree::CreateNode(ui::AXRole role) {
+  content::RenderFrame* render_frame = render_view_->GetMainRenderFrame();
+  content::RenderAccessibility* render_accessibility =
+      render_frame->GetRenderAccessibility();
+
   ui::AXNodeData* node = new ui::AXNodeData();
-  node->id = render_accessibility_->GenerateAXID();
+  node->id = render_accessibility->GenerateAXID();
   node->role = role;
   node->state = 1 << ui::AX_STATE_ENABLED | 1 << ui::AX_STATE_READ_ONLY;
   nodes_.push_back(base::WrapUnique(node));