Correctly whitelist the PDF plugin in the PDF extension.

chrome/browser/pdf/pdf_extension_util.cc

Index: chrome/browser/pdf/pdf_extension_util.cc
diff --git a/chrome/browser/pdf/pdf_extension_util.cc b/chrome/browser/pdf/pdf_extension_util.cc
index 5ef8f82d279622ec5c7cb997af67ceb236522edd..7446087740af9fda6b40f0a3aa29270c4f0980c2 100644
--- a/chrome/browser/pdf/pdf_extension_util.cc
+++ b/chrome/browser/pdf/pdf_extension_util.cc
@@ -25,6 +25,14 @@ const char kMaterialIndex[] = "index-material.html";
 
 }  // namespace
 
+// These should match the keys for the Chrome and Chromium PDF Viewer entries in
+// chrome/browser/resources/plugin_metadata/plugins_*.json.
+#if defined(GOOGLE_CHROME_BUILD)
+const char kPdfResourceIdentifier[] = "google-chrome-pdf";
+#else
+const char kPdfResourceIdentifier[] = "chromium-pdf";
+#endif
+
 std::string GetManifest() {
   std::string manifest_contents =
       ResourceBundle::GetSharedInstance().GetRawDataResource(