Do not prefill username when adding an account

chrome/browser/ui/webui/signin/inline_login_handler_impl.cc

 // Copyright 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/ui/webui/signin/inline_login_handler_impl.h"
 
 #include "base/atomic_sequence_num.h"
 #include "base/bind.h"
 #include "base/prefs/pref_service.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 48 matching lines @@
       source == signin::SOURCE_AVATAR_BUBBLE_SIGN_IN) {
     // Drop the leading slash in the path.
     params.SetString("gaiaPath",
         GaiaUrls::GetInstance()->embedded_signin_url().path().substr(1));
   }
 
   params.SetString("service", "chromiumsync");
   params.SetString("continueUrl",
       signin::GetLandingURL("source", static_cast<int>(source)).spec());
 
-  std::string last_email = Profile::FromWebUI(web_ui())->GetPrefs()->GetString(
-      prefs::kGoogleServicesLastUsername);
-  if (!last_email.empty())
-    params.SetString("email", last_email);
+  if (source != signin::SOURCE_AVATAR_BUBBLE_ADD_ACCOUNT) {
+    std::string last_email = Profile::FromWebUI(web_ui())->GetPrefs()->
+        GetString(prefs::kGoogleServicesLastUsername);
+    if (!last_email.empty())
+      params.SetString("email", last_email);
+  }
 
   std::string frame_url;
   net::GetValueForKeyInQuery(current_url, "frameUrl", &frame_url);
   if (!frame_url.empty())
     params.SetString("frameUrl", frame_url);
 
   std::string is_constrained;
   net::GetValueForKeyInQuery(current_url, "constrained", &is_constrained);
   if (!is_constrained.empty())
     params.SetString("constrained", is_constrained);
@@ skipping 180 matching lines @@
     TabStripModel* tab_strip_model = browser->tab_strip_model();
     if (tab_strip_model) {
       int index = tab_strip_model->GetIndexOfWebContents(tab);
       if (index != TabStripModel::kNoTab) {
         tab_strip_model->ExecuteContextMenuCommand(
             index, TabStripModel::CommandCloseTab);
       }
     }
   }
 }