MD Settings: avoid double pref observation on Startup Pages

chrome/browser/ui/webui/settings/md_settings_ui.cc

 // Copyright 2015 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/settings/md_settings_ui.h"
 
 #include <stddef.h>
 
 #include <string>
 
@@ skipping 105 matching lines @@
   AddLocalizedStrings(html_source, profile);
   html_source->SetDefaultResource(IDR_SETTINGS_SETTINGS_HTML);
 
   content::WebUIDataSource::Add(web_ui->GetWebContents()->GetBrowserContext(),
                                 html_source);
 }
 
 MdSettingsUI::~MdSettingsUI() {
 }
 
-void MdSettingsUI::AddSettingsPageUIHandler(
-    content::WebUIMessageHandler* handler_raw) {
-  scoped_ptr<content::WebUIMessageHandler> handler(handler_raw);
-  DCHECK(handler.get());
+void MdSettingsUI::RenderViewReused(
+    content::RenderViewHost* /*render_view_host*/) {
+  for (size_t i = 0; i < handlers_.size(); ++i)
+    handlers_[i]->RenderViewReused();

[dschuyler, 2016/03/10 21:49:49]

How about this instead?
for (auto handler : handlers_)
  handler->RenderViewReused();

[Dan Beam, 2016/03/11 00:07:12]

Done.

+}
 
-  web_ui()->AddMessageHandler(handler.release());
+void MdSettingsUI::AddSettingsPageUIHandler(SettingsPageUIHandler* handler) {
+  DCHECK(handler);

[dschuyler, 2016/03/10 21:49:49]

Would it be bad to have the same handler added twice?
Is that worth DCHECK'ing?

[Dan Beam, 2016/03/11 00:07:11]

Done.

+  handlers_.push_back(handler);
+  web_ui()->AddMessageHandler(handler);  // |handler| is owned by |web_ui()|.
 }
 
 void MdSettingsUI::DidStartProvisionalLoadForFrame(
     content::RenderFrameHost* render_frame_host,
     const GURL& validated_url,
     bool is_error_page,
     bool is_iframe_srcdoc) {
   load_start_time_ = base::Time::Now();
 }
 
 void MdSettingsUI::DocumentLoadedInFrame(
     content::RenderFrameHost* render_frame_host) {
   UMA_HISTOGRAM_TIMES("Settings.LoadDocumentTime.MD",
                       base::Time::Now() - load_start_time_);
 }
 
 void MdSettingsUI::DocumentOnLoadCompletedInMainFrame() {
   UMA_HISTOGRAM_TIMES("Settings.LoadCompletedTime.MD",
                       base::Time::Now() - load_start_time_);
 }
 
 }  // namespace settings