Various optimizations to reduce the number of temporary allocations.

chrome/browser/ui/prefs/prefs_tab_helper.cc

Index: chrome/browser/ui/prefs/prefs_tab_helper.cc
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.cc b/chrome/browser/ui/prefs/prefs_tab_helper.cc
index a3323c7ef3274677cdfa8ae29f98982d223b3ec0..ad0d91ce181f42df411addf471fd0ca4bccab050 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.cc
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.cc
@@ -129,12 +129,16 @@ ALL_FONT_SCRIPTS(WEBKIT_WEBPREFS_FONTS_STANDARD)
 void RegisterFontFamilyMapObserver(
     PrefChangeRegistrar* registrar,
     const char* map_name,
-    const PrefChangeRegistrar::NamedChangeCallback& obs) {
+    const PrefChangeRegistrar::NamedChangeCallback& obs,
+    std::string* pref_name) {
   DCHECK(StartsWithASCII(map_name, "webkit.webprefs.", true));
+  DCHECK(pref_name);
   for (size_t i = 0; i < prefs::kWebKitScriptsForFontFamilyMapsLength; ++i) {
     const char* script = prefs::kWebKitScriptsForFontFamilyMaps[i];
-    std::string pref_name = base::StringPrintf("%s.%s", map_name, script);
-    registrar->Add(pref_name.c_str(), obs);
+    pref_name->assign(map_name);
+    pref_name->append(1, '.');
+    pref_name->append(script);
+    registrar->Add(*pref_name, obs);
   }
 }
 
@@ -349,27 +353,37 @@ PrefsTabHelper::PrefsTabHelper(WebContents* contents)
       pref_change_registrar_.Add(pref_name, webkit_callback);
     }
 
+    std::string pref_name;
+    pref_name.reserve(500);
+
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitStandardFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitFixedFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitSerifFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitSansSerifFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitCursiveFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitFantasyFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitPictographFontFamilyMap,
-                                  webkit_callback);
+                                  webkit_callback,
+                                  &pref_name);
   }
 
   content::RendererPreferences* render_prefs =
@@ -614,7 +628,7 @@ void PrefsTabHelper::OnFontFamilyPrefChanged(const std::string& pref_name) {
                                              &generic_family,
                                              &script)) {
     PrefService* prefs = GetProfile()->GetPrefs();
-    std::string pref_value = prefs->GetString(pref_name.c_str());
+    std::string pref_value = prefs->GetString(pref_name);
     if (pref_value.empty()) {
       WebPreferences web_prefs =
           web_contents_->GetRenderViewHost()->GetWebkitPreferences();