Fix issue with browser action toolbar putting all extension icons in overflow once sync happens.

chrome/browser/extensions/extension_toolbar_model_browsertest.cc

 // Copyright (c) 2011 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 "base/macros.h"
 #include "chrome/browser/extensions/extension_browsertest.h"
 #include "chrome/browser/extensions/extension_toolbar_model.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/test/base/in_process_browser_test.h"
@@ skipping 566 matching lines @@
 
   // When we stop highlighting, we should see the new extension show up.
   model_->StopHighlighting();
   EXPECT_FALSE(model_->is_highlighting());
   EXPECT_EQ(3u, model_->toolbar_items().size());
   EXPECT_EQ(id_a, ExtensionAt(0)->id());
   EXPECT_EQ(id_b, ExtensionAt(1)->id());
   EXPECT_EQ(id_c, ExtensionAt(2)->id());
 }
 
+IN_PROC_BROWSER_TEST_F(ExtensionToolbarModelTest, SizeAfterPrefChange) {
+  // Load two extensions with browser action.
+  base::FilePath extension_a_path(test_data_dir_.AppendASCII("api_test")
+                                                .AppendASCII("browser_action")
+                                                .AppendASCII("basics"));
+  ASSERT_TRUE(LoadExtension(extension_a_path));
+  base::FilePath extension_b_path(test_data_dir_.AppendASCII("api_test")
+                                                .AppendASCII("browser_action")
+                                                .AppendASCII("popup"));
+  ASSERT_TRUE(LoadExtension(extension_b_path));
+  std::string id_a = ExtensionAt(0)->id();
+  std::string id_b = ExtensionAt(1)->id();
+
+  // Should be at max size (-1).
+  EXPECT_EQ(-1, model_->GetVisibleIconCount());
+
+  model_->OnExtensionToolbarPrefChange();
+
+  // Should still be at max size.
+  EXPECT_EQ(-1, model_->GetVisibleIconCount());
+}
+
 }  // namespace extensions