Temporarily re-introduce load-component-extension switch.

chrome/browser/extensions/extension_service.cc

 // Copyright (c) 2013 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.
 
 #include "chrome/browser/extensions/extension_service.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <iterator>
@@ skipping 421 matching lines @@
 
   DCHECK(!is_ready());  // Can't redo init.
   DCHECK_EQ(registry_->enabled_extensions().size(), 0u);
 
   // LoadAllExtensions() calls OnLoadedInstalledExtensions().
   component_loader_->LoadAll();
   extensions::InstalledLoader(this).LoadAllExtensions();
   LoadExtensionsFromCommandLineFlag(switches::kDisableExtensionsExcept);
   if (extensions_enabled_)
     LoadExtensionsFromCommandLineFlag(switches::kLoadExtension);
+  // TODO(samuong): Remove this when ChromeDriver stops supporting Chrome 56.
+  // ChromeDriver has no way of determining the Chrome version until after
+  // launch, so it needs to continue passing load-component-extension until it
+  // stops supporting Chrome 56.

[Devlin, 2017/02/14 20:44:41]

Clarify that this only loads the extension as a regular extension, *not* as a
component extension, and is thus safe.

[Devlin, 2017/02/14 20:44:41]

ETA?

[samuong, 2017/02/14 21:22:49]

Done. ChromeDriver supports the current and previous stable releases, so we
won't need this flag in Chrome 58+. I've updated the comment to mention this.

+  if (command_line_->HasSwitch(switches::kEnableAutomation))

[Devlin, 2017/02/14 20:44:41]

Maybe something like:
if (command_line_->HasSwitch(switches::kEnableAutomation) &&
    command_line_->HasSwitch(kLoadComponentExtension)) {
  LOG(WARNING) << "Loading extension specified by --load-component-extension as
a regular extension. Extensions specified by --load-component-extension will not
be loaded starting in M<NN>. Use --load-extension or
--disable-extensions-except."
  LoadExtensionFromCommandLineFlag(kLoadComponentExtension);
}

[samuong, 2017/02/14 21:22:49]

Done.

+    LoadExtensionsFromCommandLineFlag(switches::kLoadComponentExtension);
   EnabledReloadableExtensions();
   MaybeFinishShutdownDelayed();
   SetReadyAndNotifyListeners();
 
   // TODO(erikkay): this should probably be deferred to a future point
   // rather than running immediately at startup.
   CheckForExternalUpdates();
 
   LoadGreylistFromPrefs();
 }
@@ skipping 2043 matching lines @@
 }
 
 void ExtensionService::OnProfileDestructionStarted() {
   ExtensionIdSet ids_to_unload = registry_->enabled_extensions().GetIDs();
   for (ExtensionIdSet::iterator it = ids_to_unload.begin();
        it != ids_to_unload.end();
        ++it) {
     UnloadExtension(*it, UnloadedExtensionInfo::REASON_PROFILE_SHUTDOWN);
   }
 }