Don't use command line flags for enabling the internal pdf plugin. Instead, ...

chrome/common/chrome_switches.h

 // Copyright (c) 2010 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.
 
 // Defines all the command-line switches used by Chrome.
 
 #ifndef CHROME_COMMON_CHROME_SWITCHES_H_
 #define CHROME_COMMON_CHROME_SWITCHES_H_
 
 #include "build/build_config.h"
@@ skipping 128 matching lines @@
 extern const char kHideIcons[];
 extern const char kHomePage[];
 extern const char kHostRules[];
 extern const char kHostResolverRules[];
 extern const char kImport[];
 extern const char kImportFromFile[];
 extern const char kInProcessPlugins[];
 extern const char kInProcessWebGL[];
 extern const char kIncognito[];
 extern const char kInternalNaCl[];
-extern const char kInternalPDF[];
 extern const char kInternalPepper[];
 extern const char kJavaScriptFlags[];
 extern const char kLoadExtension[];
 extern const char kLoadPlugin[];
 extern const char kLongLivedExtensions[];
 extern const char kLogFilterPrefix[];
 extern const char kLogPluginMessages[];
 extern const char kLoggingLevel[];
 extern const char kMakeDefaultBrowser[];
 extern const char kMediaCacheSize[];
@@ skipping 133 matching lines @@
 #endif
 // Return true if the switches indicate the seccomp sandbox is enabled.
 bool SeccompSandboxEnabled();
 
 // DON'T ADD RANDOM STUFF HERE. Put it in the main section above in
 // alphabetical order, or in one of the ifdefs (also in order in each section).
 
 }  // namespace switches
 
 #endif  // CHROME_COMMON_CHROME_SWITCHES_H_