MD Settings: avoid double pref observation on Startup Pages

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

Index: chrome/browser/ui/webui/settings/md_settings_ui.h
diff --git a/chrome/browser/ui/webui/settings/md_settings_ui.h b/chrome/browser/ui/webui/settings/md_settings_ui.h
index 301f4f25c38269f754eac18ed208f54778c377b5..72ca4f3c2df24779425087b31a8ef33c8df9a06a 100644
--- a/chrome/browser/ui/webui/settings/md_settings_ui.h
+++ b/chrome/browser/ui/webui/settings/md_settings_ui.h
@@ -27,6 +27,9 @@ class SettingsPageUIHandler : public content::WebUIMessageHandler {
   // WebUIMessageHandler implementation.
   void RegisterMessages() override {}
 
+  // TODO(dbeam): move to WebUIMessageHandler?
+  virtual void RenderViewReused() {}
+
  protected:
   // Helper method for responding to JS requests initiated with
   // cr.sendWithPromise(), for the case where the returned promise should be
@@ -51,6 +54,9 @@ class MdSettingsUI : public content::WebUIController,
   explicit MdSettingsUI(content::WebUI* web_ui);
   ~MdSettingsUI() override;
 
+  // Overridden from content::WebUIController:

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

s/:/./

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

following the code below, as per the style guide:

"""
Parting Words

Use common sense and BE CONSISTENT.

If you are editing code, take a few minutes to look at the code around you and
determine its style. If they use spaces around their if clauses, you should,
too. If their comments have little boxes of stars around them, make your
comments have little boxes of stars around them too.
"""

+  void RenderViewReused(content::RenderViewHost* render_view_host) override;
+
   // Overridden from content::WebContentsObserver:
   void DidStartProvisionalLoadForFrame(
       content::RenderFrameHost* render_frame_host,
@@ -62,7 +68,10 @@ class MdSettingsUI : public content::WebUIController,
   void DocumentOnLoadCompletedInMainFrame() override;
 
  private:
-  void AddSettingsPageUIHandler(content::WebUIMessageHandler* handler);
+  void AddSettingsPageUIHandler(SettingsPageUIHandler* handler);
+
+  // Weak references; all |handlers_| are owned by |web_ui()|.
+  std::vector<SettingsPageUIHandler*> handlers_;
 
   base::Time load_start_time_;