Bug 22554: Don't set Battery API pref anymore

Mozilla made the Battery API chrome-only
(https://bugzilla.mozilla.org/show_bug.cgi?id=1313580). We therefore
don't need to take care of it anymore in Torbutton.

src/chrome/content/torbutton.js

@@ -1732,7 +1732,6 @@ function torbutton_update_fingerprinting_prefs() {
 
     m_tb_prefs.setBoolPref("webgl.min_capability_mode", mode);
     m_tb_prefs.setBoolPref("webgl.disable-extensions", mode);
-    m_tb_prefs.setBoolPref("dom.battery.enabled", !mode);
     m_tb_prefs.setBoolPref("dom.network.enabled", !mode);
     m_tb_prefs.setBoolPref("dom.enable_performance", !mode);
     m_tb_prefs.setBoolPref("plugin.expose_full_path", !mode);

src/chrome/locale/en/torbutton.dtd

@@ -30,7 +30,7 @@
 <!ENTITY torbutton.prefs.restrict_thirdparty_tooltip "Keep this box checked to prevent various browser features from being abused to track you as you browse the web. Modified features include blob URLs, broadcast channels, the browser cache, cookies, favicons, HTTP Auth headers, link preconnects, localStorage, mediaSource URLs, OCSP requests, SharedWorkers, and TLS session tickets.">
 <!ENTITY torbutton.prefs.resist_fingerprinting "Change details that distinguish you from other Tor Browser users">
 <!ENTITY torbutton.prefs.resist_fingerprinting.accesskey "F">
-<!ENTITY torbutton.prefs.resist_fingerprinting_tooltip "Keep this box checked to hide things from websites that could be unique about you, including your battery status, computer performance, keyboard layout, locale, the location of installed plugins, the list of installed plugins, your network status, screen orientation, screen size, site-specific zoom levels, supported file types, system colors, and WebGL capabilities.">
+<!ENTITY torbutton.prefs.resist_fingerprinting_tooltip "Keep this box checked to hide things from websites that could be unique about you, including your computer performance, keyboard layout, locale, the location of installed plugins, the list of installed plugins, your network status, screen orientation, screen size, site-specific zoom levels, supported file types, system colors, and WebGL capabilities.">
 <!ENTITY torbutton.prefs.sec_caption "Security Level">
 <!ENTITY torbutton.prefs.sec_caption_tooltip "The Security Slider lets you disable certain browser features that may make your browser more vulnerable to hacking attempts.">
 <!ENTITY torbutton.prefs.sec_low "Low (default)">