Merge branch 'charlesmchen/themeConcurrency'

SignalMessaging/appearance/Theme.h

@@ -13,7 +13,7 @@ extern NSString *const ThemeDidChangeNotification;
 
 - (instancetype)init NS_UNAVAILABLE;
 
-@property (class, readonly, nonatomic) BOOL isDarkThemeEnabled;
+@property (class, readonly, atomic) BOOL isDarkThemeEnabled;
 
 + (void)setIsDarkThemeEnabled:(BOOL)value;
 

SignalMessaging/appearance/Theme.m

@@ -20,8 +20,6 @@ NSString *const ThemeKeyThemeEnabled = @"ThemeKeyThemeEnabled";
 
 + (BOOL)isDarkThemeEnabled
 {
-    OWSAssertIsOnMainThread();
-
     if (!CurrentAppContext().isMainApp) {
         // Ignore theme in app extensions.
         return NO;