Clean up defensive TabManager handling

chrome/browser/extensions/api/tabs/tabs_test.cc

 // Copyright (c) 2012 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 <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
@@ skipping 1299 matching lines @@
           function.get(), base::StringPrintf("[%u, {\"code\": \"true\"}]",
                                              api::windows::WINDOW_ID_CURRENT),
           DevToolsWindowTesting::Get(devtools)->browser()),
       manifest_errors::kCannotAccessPageWithUrl));
 
   DevToolsWindowTesting::CloseDevToolsWindowSync(devtools);
 }
 
 // TODO(georgesak): change this browsertest to an unittest.
 IN_PROC_BROWSER_TEST_F(ExtensionTabsTest, DiscardedProperty) {
-  ASSERT_TRUE(g_browser_process && g_browser_process->GetTabManager());

[Devlin, 2016/08/16 16:10:50]

This seems reasonable to keep, since it helps ensure that what we know to be
true now remains true. :)

[Anderson Silva, 2016/08/16 17:26:12]

Done.

   memory::TabManager* tab_manager = g_browser_process->GetTabManager();
 
   // Create two aditional tabs.
   content::OpenURLParams params(GURL(url::kAboutBlankURL), content::Referrer(),
                                 NEW_BACKGROUND_TAB, ui::PAGE_TRANSITION_LINK,
                                 false);
   content::WebContents* web_contents_a = browser()->OpenURL(params);
   content::WebContents* web_contents_b = browser()->OpenURL(params);
 
   // Set up query function with an extension.
@@ skipping 783 matching lines @@
   EXPECT_TRUE(
       base::MatchPattern(error, manifest_errors::kCannotAccessChromeUrl));
 
   // chrome.tabs.setZoomSettings().
   error = RunSetZoomSettingsExpectError(tab_id, "manual", "per-tab");
   EXPECT_TRUE(
       base::MatchPattern(error, manifest_errors::kCannotAccessChromeUrl));
 }
 
 }  // namespace extensions