Clean up defensive TabManager handling

chrome/browser/memory/tab_manager.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 "chrome/browser/memory/tab_manager.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 465 matching lines @@
 
 void TabManager::OnAutoDiscardableStateChange(content::WebContents* contents,
                                               bool is_auto_discardable) {
   FOR_EACH_OBSERVER(
       TabManagerObserver, observers_,
       OnAutoDiscardableStateChange(contents, is_auto_discardable));
 }
 
 // static
 void TabManager::PurgeMemoryAndDiscardTab() {
-  if (g_browser_process && g_browser_process->GetTabManager()) {
-    TabManager* manager = g_browser_process->GetTabManager();
-    manager->PurgeBrowserMemory();
-    manager->DiscardTab();
-  }
+  TabManager* manager = g_browser_process->GetTabManager();
+  manager->PurgeBrowserMemory();
+  manager->DiscardTab();
 }
 
 // static
 bool TabManager::IsInternalPage(const GURL& url) {
   // There are many chrome:// UI URLs, but only look for the ones that users
   // are likely to have open. Most of the benefit is the from NTP URL.
   const char* const kInternalPagePrefixes[] = {
       chrome::kChromeUIDownloadsURL, chrome::kChromeUIHistoryURL,
       chrome::kChromeUINewTabURL, chrome::kChromeUISettingsURL,
   };
@@ skipping 437 matching lines @@
   // platform.
   std::string allow_multiple_discards = variations::GetVariationParamValue(
       features::kAutomaticTabDiscarding.name, "AllowMultipleDiscards");
   return (allow_multiple_discards != "true");
 #else
   return false;
 #endif
 }
 
 }  // namespace memory