Bug 1527811 - Add GMPUtils._isWindowsOnARM64(). r=Gijs

Allows subsequent patches to special case behavior when running on
Windows on ARM64.

Differential Revision: https://phabricator.services.mozilla.com/D19899

--HG--
extra : source : 44e24c6d7a695e2a8ab5d1c2451f1fbf4d5d996f
extra : intermediate-source : 67cc92a41638ec58b5c54e871b0e5eede698c92e
extra : histedit_source : b2cca3608baf5b49228741877d4e5b5c4e3fa575

toolkit/modules/GMPUtils.jsm

@@ -12,6 +12,7 @@ var EXPORTED_SYMBOLS = [ "GMP_PLUGIN_IDS",
 
 const {Services} = ChromeUtils.import("resource://gre/modules/Services.jsm");
 const {AppConstants} = ChromeUtils.import("resource://gre/modules/AppConstants.jsm");
+const {UpdateUtils} = ChromeUtils.import("resource://gre/modules/UpdateUtils.jsm");
 
 // GMP IDs
 const OPEN_H264_ID  = "gmp-gmpopenh264";
@@ -95,6 +96,10 @@ var GMPUtils = {
   _isPluginForceSupported(aPlugin) {
     return GMPPrefs.getBool(GMPPrefs.KEY_PLUGIN_FORCE_SUPPORTED, false, aPlugin.id);
   },
+
+  _isWindowsOnARM64() {
+    return AppConstants.platform == "win" && UpdateUtils.ABI.match(/aarch64/);
+  },
 };
 
 /**