Guard against the app launcher having a custom start page URL.

chrome/browser/ui/app_list/start_page_service.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/app_list/start_page_service.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/command_line.h"
@@ skipping 119 matching lines @@
   observers_.AddObserver(observer);
 }
 
 void StartPageService::RemoveObserver(StartPageObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
 void StartPageService::AppListShown() {
   if (!contents_) {
     LoadContents();
-  } else {
+  } else if (contents_->GetWebUI()) {
     // If experimental hotwording is enabled, don't enable hotwording in the
     // start page, since the hotword extension is taking care of this.
     bool hotword_enabled = HotwordEnabled() &&
         !HotwordService::IsExperimentalHotwordingEnabled();
     contents_->GetWebUI()->CallJavascriptFunction(
         "appList.startPage.onAppListShown",
         base::FundamentalValue(hotword_enabled));
   }
 }
 
 void StartPageService::AppListHidden() {
-  contents_->GetWebUI()->CallJavascriptFunction(
-      "appList.startPage.onAppListHidden");
+  if (contents_->GetWebUI()) {
+    contents_->GetWebUI()->CallJavascriptFunction(
+        "appList.startPage.onAppListHidden");
+  }
   if (!app_list::switches::IsExperimentalAppListEnabled())
     UnloadContents();
 }
 
 void StartPageService::ToggleSpeechRecognition() {
   DCHECK(contents_);
   speech_button_toggled_manually_ = true;
+  if (!contents_->GetWebUI())
+    return;
+
   if (webui_finished_loading_) {
     contents_->GetWebUI()->CallJavascriptFunction(
         "appList.startPage.toggleSpeechRecognition");
   } else {
     pending_webui_callbacks_.push_back(
         base::Bind(&StartPageService::ToggleSpeechRecognition,
                    base::Unretained(this)));
   }
 }
 
@@ skipping 97 matching lines @@
       ui::PAGE_TRANSITION_AUTO_TOPLEVEL,
       std::string());
 }
 
 void StartPageService::UnloadContents() {
   contents_.reset();
   webui_finished_loading_ = false;
 }
 
 }  // namespace app_list