Fix Appearance module when using Chrome Debugger

Summary:
The appearance module uses sync native module methods which doesn't work with the chrome debugger. This broke in 0.62: https://github.com/facebook/react-native/issues/26705

This fix makes the appearance module return 'light' when using the chrome debugger.

Changelog: [Fixed] Appearance `getColorScheme` no longer breaks the debugger

Reviewed By: yungsters

Differential Revision: D20879779

fbshipit-source-id: ad49c66226096433bc9f270e004ad4a6f54fa8c2

Libraries/Utilities/Appearance.js

@@ -17,6 +17,7 @@ import NativeAppearance, {
   type ColorSchemeName,
 } from './NativeAppearance';
 import invariant from 'invariant';
+import {isAsyncDebugging} from './DebugEnvironment';
 
 type AppearanceListener = (preferences: AppearancePreferences) => void;
 const eventEmitter = new EventEmitter();
@@ -50,6 +51,14 @@ module.exports = {
    * @returns {?ColorSchemeName} Value for the color scheme preference.
    */
   getColorScheme(): ?ColorSchemeName {
+    if (__DEV__) {
+      if (isAsyncDebugging) {
+        // Hard code light theme when using the async debugger as
+        // sync calls aren't supported
+        return 'light';
+      }
+    }
+
     // TODO: (hramos) T52919652 Use ?ColorSchemeName once codegen supports union
     const nativeColorScheme: ?string =
       NativeAppearance == null