Create a define for the gyp variable internal_pdf.

chrome/common/pepper_plugin_registry.cc

Index: chrome/common/pepper_plugin_registry.cc
diff --git a/chrome/common/pepper_plugin_registry.cc b/chrome/common/pepper_plugin_registry.cc
index 7caf9c9403bcc9cc3e41b20258230d545872f060..e246b5ad096220eba4706024451324e41967b32f 100644
--- a/chrome/common/pepper_plugin_registry.cc
+++ b/chrome/common/pepper_plugin_registry.cc
@@ -101,6 +101,7 @@ void PepperPluginRegistry::GetPluginInfoFromSwitch(
 // static
 void PepperPluginRegistry::GetExtraPlugins(
     std::vector<PepperPluginInfo>* plugins) {
+#if defined(INTERNAL_PDF)
   FilePath path;
   // We can't check for path existance here, since we are in the sandbox.
   // If plugin is missing, it will later fail to
@@ -114,6 +115,7 @@ void PepperPluginRegistry::GetExtraPlugins(
     pdf.type_descriptions = "Portable Document Format";
     plugins->push_back(pdf);
   }
+#endif  // INTERNAL_PDF
 }
 
 PepperPluginRegistry::InternalPluginInfo::InternalPluginInfo() {