Remove the unused parts of PPB_PDF

ppapi/tests/test_pdf.h

 // Copyright (c) 2012 The Chromium 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 PAPPI_TESTS_TEST_PDF_H_
 #define PAPPI_TESTS_TEST_PDF_H_
 
 #include <string>
 
 #include "ppapi/c/pp_stdint.h"
 #include "ppapi/tests/test_case.h"
 
 class TestPDF : public TestCase {
  public:
   explicit TestPDF(TestingInstance* instance);
 
   // TestCase implementation.
   virtual void RunTests(const std::string& filter);
 
  private:
   std::string TestGetLocalizedString();
-  std::string TestGetResourceImage();
   std::string TestGetV8ExternalSnapshotData();
 };
 
 #endif  // PAPPI_TESTS_TEST_PDF_H_