Get native theme through IPC not remote

ts/test-electron/context/NativeThemeListener_test.ts

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+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import { EventEmitter } from 'events';
+
+import {
+  NativeThemeListener,
+  MinimalIPC,
+  SystemThemeHolder,
+} from '../../context/NativeThemeListener';
+import { NativeThemeState } from '../../types/NativeThemeNotifier.d';
+
+class FakeIPC extends EventEmitter implements MinimalIPC {
+  constructor(private readonly state: NativeThemeState) {
+    super();
+  }
+
+  public sendSync(channel: string) {
+    assert.strictEqual(channel, 'native-theme:init');
+    return this.state;
+  }
+}
+
+describe('NativeThemeListener', () => {
+  const holder: SystemThemeHolder = { systemTheme: 'dark' };
+
+  it('syncs the initial native theme', () => {
+    const dark = new NativeThemeListener(
+      new FakeIPC({
+        shouldUseDarkColors: true,
+      }),
+      holder
+    );
+
+    assert.strictEqual(holder.systemTheme, 'dark');
+    assert.isTrue(dark.theme.shouldUseDarkColors);
+
+    const light = new NativeThemeListener(
+      new FakeIPC({
+        shouldUseDarkColors: false,
+      }),
+      holder
+    );
+
+    assert.strictEqual(holder.systemTheme, 'light');
+    assert.isFalse(light.theme.shouldUseDarkColors);
+  });
+
+  it('should react to native theme changes', () => {
+    const ipc = new FakeIPC({
+      shouldUseDarkColors: true,
+    });
+
+    const listener = new NativeThemeListener(ipc, holder);
+
+    ipc.emit('native-theme:changed', null, <NativeThemeState>{
+      shouldUseDarkColors: false,
+    });
+
+    assert.strictEqual(holder.systemTheme, 'light');
+    assert.isFalse(listener.theme.shouldUseDarkColors);
+  });
+
+  it('should notify subscribers of native theme changes', done => {
+    const ipc = new FakeIPC({
+      shouldUseDarkColors: true,
+    });
+
+    const listener = new NativeThemeListener(ipc, holder);
+
+    listener.subscribe(state => {
+      assert.isFalse(state.shouldUseDarkColors);
+      done();
+    });
+
+    ipc.emit('native-theme:changed', null, <NativeThemeState>{
+      shouldUseDarkColors: false,
+    });
+  });
+});