Move ".crx"/".pem" constants and extension_filenames constants into extensions/common/constants.cc.

chrome/browser/download/chrome_download_manager_delegate.cc

Index: chrome/browser/download/chrome_download_manager_delegate.cc
diff --git a/chrome/browser/download/chrome_download_manager_delegate.cc b/chrome/browser/download/chrome_download_manager_delegate.cc
index 733134927b430bbdffcbc1ff18167b8746db0fd7..70e69a8de457898dbbfa56a238c8158f1460faf7 100644
--- a/chrome/browser/download/chrome_download_manager_delegate.cc
+++ b/chrome/browser/download/chrome_download_manager_delegate.cc
@@ -34,12 +34,12 @@
 #include "chrome/browser/platform_util.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/safe_browsing/safe_browsing_service.h"
-#include "chrome/common/extensions/extension.h"
 #include "chrome/common/pref_names.h"
 #include "components/user_prefs/pref_registry_syncable.h"
 #include "content/public/browser/download_item.h"
 #include "content/public/browser/download_manager.h"
 #include "content/public/browser/notification_source.h"
+#include "extensions/common/constants.h"
 
 #if defined(OS_CHROMEOS)
 #include "chrome/browser/chromeos/drive/download_handler.h"
@@ -231,7 +231,7 @@ bool ChromeDownloadManagerDelegate::ShouldOpenFileBasedOnExtension(
   // TODO(asanka): This determination is done based on |path|, while
   // ShouldOpenDownload() detects extension downloads based on the
   // characteristics of the download. Reconcile this. http://crbug.com/167702
-  if (extensions::Extension::IsExtension(path))
+  if (path.MatchesExtension(extensions::kExtensionFileExtension))
     return false;
   return download_prefs_->IsAutoOpenEnabledBasedOnExtension(path);
 }