Add private PPAPI interfaces for PDFium accessibility.

ppapi/thunk/ppb_pdf_api.h

Index: ppapi/thunk/ppb_pdf_api.h
diff --git a/ppapi/thunk/ppb_pdf_api.h b/ppapi/thunk/ppb_pdf_api.h
index 928c8cdc9fe0966c63b4280d4b5e9667f58987c3..4f24d52327b37e415a72a474070ba575df43e75f 100644
--- a/ppapi/thunk/ppb_pdf_api.h
+++ b/ppapi/thunk/ppb_pdf_api.h
@@ -32,7 +32,14 @@ class PPB_PDF_API {
                                          int* natives_size_out,
                                          const char** snapshot_data_out,
                                          int* snapshot_size_out) = 0;
-
+  virtual void SetAccessibilityViewportInfo(
+      PP_PrivateAccessibilityViewportInfo* viewport_info) = 0;
+  virtual void SetAccessibilityDocInfo(
+      PP_PrivateAccessibilityDocInfo* doc_info) = 0;
+  virtual void SetAccessibilityPageInfo(
+      PP_PrivateAccessibilityPageInfo* page_info,
+      PP_PrivateAccessibilityTextRunInfo text_runs[],
+      PP_PrivateAccessibilityCharInfo chars[]) = 0;
   static const SingletonResourceID kSingletonResourceID = PDF_SINGLETON_ID;
 };