Adds a pref and a policy to decide if PDFs should always be opened externally.

chrome/browser/download/download_prefs.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 CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_
 
 #include <set>
 
 #include "base/files/file_path.h"
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "components/prefs/pref_member.h"
 
 class PrefService;
 class Profile;
 
 namespace content {
 class BrowserContext;
 class DownloadManager;
@@ skipping 59 matching lines @@
   void DisableAutoOpenBasedOnExtension(const base::FilePath& file_name);
 
 #if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_MACOSX)
   // Store the user preference to disk. If |should_open| is true, also disable
   // the built-in PDF plugin. If |should_open| is false, enable the PDF plugin.
   void SetShouldOpenPdfInSystemReader(bool should_open);
 
   // Return whether the user prefers to open PDF downloads in the platform's
   // default reader.
   bool ShouldOpenPdfInSystemReader() const;
+
+  // Used by tests to disable version checks for Adobe.
+  void DisableAdobeVersionCheckForTests();
 #endif
 
+
   void ResetAutoOpen();
 
  private:
   void SaveAutoOpenState();
 
   Profile* profile_;
 
   BooleanPrefMember prompt_for_download_;
   FilePathPrefMember download_path_;
   FilePathPrefMember save_file_path_;
   IntegerPrefMember save_file_type_;
 
   // Set of file extensions to open at download completion.
   struct AutoOpenCompareFunctor {
     bool operator()(const base::FilePath::StringType& a,
                     const base::FilePath::StringType& b) const;
   };
   typedef std::set<base::FilePath::StringType,
                    AutoOpenCompareFunctor> AutoOpenSet;
   AutoOpenSet auto_open_;
 
 #if defined(OS_WIN) || defined(OS_LINUX) || defined(OS_MACOSX)
   bool should_open_pdf_in_system_reader_;
+  bool disable_adobe_version_check_for_tests_;

[asanka, 2016/09/30 14:34:53]

Rather than disable the version check, can we force the test to succeed? I.e.
Make adobe_reader_info_win.h: IsAdobeReaderUptodate() and
IsAdobeReaderDefaultPDFViewer() overridable for testing?

This way the effects of the Adobe reader version check will be uniform rather
than just being overridden here. 

[pastarmovj, 2016/10/04 10:06:34]

I agree with your comment but for the sake of expediting this CL into the
current version and due to lack of other direct use cases of this I would like
to make this work a separate issue and filed crbug/652624 are you ok with that?

 #endif
 
   DISALLOW_COPY_AND_ASSIGN(DownloadPrefs);
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_PREFS_H_