Retrieve test data directory at run time

testing/embedder_test.h

 // Copyright (c) 2015 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef TESTING_EMBEDDER_TEST_H_
 #define TESTING_EMBEDDER_TEST_H_
 
 #include <map>
 #include <string>
 
@@ skipping 62 matching lines @@
 
   void SetDelegate(Delegate* delegate) {
     delegate_ = delegate ? delegate : default_delegate_.get();
   }
 
   FPDF_DOCUMENT document() { return document_; }
   FPDF_FORMHANDLE form_handle() { return form_handle_; }
 
   // Open the document specified by |filename|, and create its form fill
   // environment, or return false on failure.
+  // The filename is relative to the test data directory where we store all the
+  // test files.
   virtual bool OpenDocument(const std::string& filename,
                             bool must_linearize = false);
 
   // Perform JavaScript actions that are to run at document open time.
   virtual void DoOpenActions();
 
   // Determine the page numbers present in the document.
   virtual int GetFirstPageNum();
   virtual int GetPageCount();
 
@@ skipping 40 matching lines @@
   static int SetTimerTrampoline(FPDF_FORMFILLINFO* info,
                                 int msecs,
                                 TimerCallback fn);
   static void KillTimerTrampoline(FPDF_FORMFILLINFO* info, int id);
   static FPDF_PAGE GetPageTrampoline(FPDF_FORMFILLINFO* info,
                                      FPDF_DOCUMENT document,
                                      int page_index);
 };
 
 #endif  // TESTING_EMBEDDER_TEST_H_