Android: disables observing changes for font prefs.

chrome/browser/ui/prefs/prefs_tab_helper.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/ui/prefs/prefs_tab_helper.h"
 
 #include <string>
 
 #include "base/prefs/overlay_user_pref_store.h"
 #include "base/prefs/pref_service.h"
@@ skipping 120 matching lines @@
     const char* pref_name = pref_name_str.c_str();
     if (fonts_with_defaults.find(pref_name) == fonts_with_defaults.end()) {
       // We haven't already set a default value for this font preference, so set
       // an empty string as the default.
       registry->RegisterStringPref(
           pref_name, "", PrefRegistrySyncable::UNSYNCABLE_PREF);
     }
   }
 }
 
+#if !defined(OS_ANDROID)
 // Registers |obs| to observe per-script font prefs under the path |map_name|.
+// On android, there's no exposed way to change these prefs, so we can save
+// ~715KB of heap and some startup cycles by avoiding observing these prefs
+// since they will never change.
 void RegisterFontFamilyMapObserver(
     PrefChangeRegistrar* registrar,
     const char* map_name,
     const PrefChangeRegistrar::NamedChangeCallback& obs) {
   DCHECK(StartsWithASCII(map_name, "webkit.webprefs.", true));
   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);
   }
 }
+#endif  // !defined(OS_ANDROID)
 
 struct FontDefault {
   const char* pref_name;
   int resource_id;
 };
 
 // Font pref defaults.  The prefs that have defaults vary by platform, since not
 // all platforms have fonts for all scripts for all generic families.
 // TODO(falken): add proper defaults when possible for all
 // platforms/scripts/generic families.
@@ skipping 217 matching lines @@
 
     PrefChangeRegistrar::NamedChangeCallback webkit_callback = base::Bind(
         &PrefsTabHelper::OnWebPrefChanged, base::Unretained(this));
     for (int i = 0; i < kPrefsToObserveLength; ++i) {
       const char* pref_name = kPrefsToObserve[i];
       DCHECK(std::string(pref_name) == prefs::kDefaultCharset ||
              StartsWithASCII(pref_name, "webkit.webprefs.", true));
       pref_change_registrar_.Add(pref_name, webkit_callback);
     }
 
+#if !defined(OS_ANDROID)
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitStandardFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitFixedFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitSerifFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitSansSerifFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitCursiveFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitFantasyFontFamilyMap,
                                   webkit_callback);
     RegisterFontFamilyMapObserver(&pref_change_registrar_,
                                   prefs::kWebKitPictographFontFamilyMap,
                                   webkit_callback);
+#endif  // !defined(OS_ANDROID)
   }
 
   renderer_preferences_util::UpdateFromSystemSettings(
       web_contents_->GetMutableRendererPrefs(), GetProfile());
 
   registrar_.Add(this, chrome::NOTIFICATION_USER_STYLE_SHEET_UPDATED,
                  content::NotificationService::AllSources());
 #if defined(OS_POSIX) && !defined(OS_MACOSX) && defined(ENABLE_THEMES)
   registrar_.Add(this, chrome::NOTIFICATION_BROWSER_THEME_CHANGED,
                  content::Source<ThemeService>(
@@ skipping 233 matching lines @@
       WebPreferences web_prefs =
           web_contents_->GetRenderViewHost()->GetWebkitPreferences();
       OverrideFontFamily(&web_prefs, generic_family, script, "");
       web_contents_->GetRenderViewHost()->UpdateWebkitPreferences(web_prefs);
       return;
     }
   }
 
   UpdateWebPreferences();
 }