Bug 1149780 - Uncomment code block that depends on SDK 17 & delete try-catch block that uses reflection. r=jchen

mobile/android/base/java/org/mozilla/gecko/mozglue/GeckoLoader.java

@@ -162,10 +162,7 @@ public final class GeckoLoader {
         f = context.getCacheDir();
         putenv("CACHE_DIRECTORY=" + f.getPath());
 
-        /* We really want to use this code, but it requires bumping up the SDK to 17 so for now
-           we will use reflection. See https://bugzilla.mozilla.org/show_bug.cgi?id=811763#c11
-
-        if (Build.VERSION.SDK_INT >= 17) {
+        if (AppConstants.Versions.feature17Plus) {
             android.os.UserManager um = (android.os.UserManager)context.getSystemService(Context.USER_SERVICE);
             if (um != null) {
                 putenv("MOZ_ANDROID_USER_SERIAL_NUMBER=" + um.getSerialNumberForUser(android.os.Process.myUserHandle()));
@@ -173,21 +170,6 @@ public final class GeckoLoader {
                 Log.d(LOGTAG, "Unable to obtain user manager service on a device with SDK version " + Build.VERSION.SDK_INT);
             }
         }
-        */
-        try {
-            Object userManager = context.getSystemService("user");
-            if (userManager != null) {
-                // if userManager is non-null that means we're running on 4.2+ and so the rest of this
-                // should just work
-                Object userHandle = android.os.Process.class.getMethod("myUserHandle", (Class[])null).invoke(null);
-                Object userSerial = userManager.getClass().getMethod("getSerialNumberForUser", userHandle.getClass()).invoke(userManager, userHandle);
-                putenv("MOZ_ANDROID_USER_SERIAL_NUMBER=" + userSerial.toString());
-            }
-        } catch (Exception e) {
-            // Guard against any unexpected failures
-            Log.d(LOGTAG, "Unable to set the user serial number", e);
-        }
-
         setupLocaleEnvironment();
 
         // We don't need this any more.