Skip per-script font preferences registration and filling on Android.

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 @@
   prefs::kWebKitLoadsImagesAutomatically,
   prefs::kWebKitMinimumFontSize,
   prefs::kWebKitMinimumLogicalFontSize,
   prefs::kWebKitPluginsEnabled,
   prefs::kWebkitTabsToLinks,
   prefs::kWebKitUsesUniversalDetector
 };
 
 const int kPrefsToObserveLength = arraysize(kPrefsToObserve);
 
+#if !defined(OS_ANDROID)
 // Registers a preference under the path |pref_name| for each script used for
 // per-script font prefs.
 // For example, for WEBKIT_WEBPREFS_FONTS_SERIF ("fonts.serif"):
 // "fonts.serif.Arab", "fonts.serif.Hang", etc. are registered.
 // |fonts_with_defaults| contains all |pref_names| already registered since they
 // have a specified default value.
+// On Android there are no default values for these properties and there is no
+// way to set them, so we can avoid registering them altogether.

[falken, 2013/10/17 12:23:29]

Maybe mention that the way to set them on other platforms is through the
extension API, something like:
"On Android, the prefs have no default values and as there are no extensions the
Font Settings API cannot be used to set them, so we can avoid registering them
altogether."

[ppi, 2013/10/17 16:49:04]

Done.

 void RegisterFontFamilyPrefs(user_prefs::PrefRegistrySyncable* registry,
                              const std::set<std::string>& fonts_with_defaults) {
 
   // Expand the font concatenated with script name so this stays at RO memory
   // rather than allocated in heap.
   static const char* const kFontFamilyMap[] = {
 #define EXPAND_SCRIPT_FONT(map_name, script_name) map_name "." script_name,
 
 #include "chrome/common/pref_font_script_names-inl.h"
 ALL_FONT_SCRIPTS(WEBKIT_WEBPREFS_FONTS_CURSIVE)
@@ skipping 13 matching lines @@
       // We haven't already set a default value for this font preference, so set
       // an empty string as the default.
       registry->RegisterStringPref(
           pref_name,
           std::string(),
           user_prefs::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) {
@@ skipping 414 matching lines @@
     // not be really critical after all.
     if (browser_script != pref_script) {
       registry->RegisterLocalizedStringPref(
           pref.pref_name,
           pref.resource_id,
           user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
       fonts_with_defaults.insert(pref.pref_name);
     }
   }
 
-  // Register font prefs that don't have defaults.
+  // Register per-script font prefs that don't have defaults.
+#if !defined(OS_ANDROID)
   RegisterFontFamilyPrefs(registry, fonts_with_defaults);
+#endif
 
   registry->RegisterLocalizedIntegerPref(
       prefs::kWebKitDefaultFontSize,
       IDS_DEFAULT_FONT_SIZE,
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterLocalizedIntegerPref(
       prefs::kWebKitDefaultFixedFontSize,
       IDS_DEFAULT_FIXED_FONT_SIZE,
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterLocalizedIntegerPref(
@@ skipping 90 matching lines @@
       WebPreferences web_prefs =
           web_contents_->GetRenderViewHost()->GetWebkitPreferences();
       OverrideFontFamily(&web_prefs, generic_family, script, std::string());
       web_contents_->GetRenderViewHost()->UpdateWebkitPreferences(web_prefs);
       return;
     }
   }
 
   UpdateWebPreferences();
 }