Add private PPAPI interfaces for PDFium accessibility.

ppapi/proxy/pdf_resource.h

Index: ppapi/proxy/pdf_resource.h
diff --git a/ppapi/proxy/pdf_resource.h b/ppapi/proxy/pdf_resource.h
index 4420cc70bd66d3e5c95dd48025b83da45ea17ba5..a08e44049500babf287a4d29c6deb1d9ff9a29f5 100644
--- a/ppapi/proxy/pdf_resource.h
+++ b/ppapi/proxy/pdf_resource.h
@@ -54,6 +54,14 @@ class PPAPI_PROXY_EXPORT PDFResource
                                  int* natives_size_out,
                                  const char** snapshot_data_out,
                                  int* snapshot_size_out) override;
+  void SetAccessibilityViewportInfo(
+      PP_PrivateAccessibilityViewportInfo* viewport_info) override;
+  void SetAccessibilityDocInfo(
+      PP_PrivateAccessibilityDocInfo* doc_info) override;
+  void SetAccessibilityPageInfo(
+      PP_PrivateAccessibilityPageInfo* page_info,
+      PP_PrivateAccessibilityTextRunInfo text_runs[],
+      PP_PrivateAccessibilityCharInfo chars[]) override;
 
  private:
   std::string locale_;