test: improve browser window layout coverage (#51189)

* test: browser window webContents viewport matches content bounds

* test: browser window webContents same after vibrancy change

* fixup! test: browser window webContents viewport matches content bounds

* refactor: extract-method helper getViewportSize()

* refactor: remove non-spec change

* chore: more accurate naming

spec/api-browser-window-spec.ts

@@ -67,6 +67,9 @@ const isBeforeUnload = (event: Event, level: number, message: string) => {
   return message === 'beforeunload';
 };
 
+const getViewportSize = (w: BrowserWindow) =>
+  w.webContents.executeJavaScript('[window.innerWidth, window.innerHeight]');
+
 describe('BrowserWindow module', () => {
   it('sets the correct class name on the prototype', () => {
     expect(BrowserWindow.prototype.constructor.name).to.equal('BrowserWindow');
@@ -3141,6 +3144,17 @@ describe('BrowserWindow module', () => {
         w.setVibrancy('i-am-not-a-valid-vibrancy-type' as any);
       }).to.not.throw();
     });
+
+    it('preserves the web content viewport after setting vibrancy', async () => {
+      const w = new BrowserWindow({ show: true, width: 800, height: 600 });
+
+      await w.loadURL('about:blank');
+      const contentSize = w.getContentSize();
+      expect(await getViewportSize(w)).to.deep.equal(contentSize);
+
+      w.setVibrancy('titlebar');
+      expect(await getViewportSize(w)).to.deep.equal(contentSize);
+    });
   });
 
   ifdescribe(process.platform === 'darwin')('trafficLightPosition', () => {
@@ -3439,6 +3453,16 @@ describe('BrowserWindow module', () => {
     });
   });
 
+  describe('post-construction web content viewport', () => {
+    afterEach(closeAllWindows);
+    it('matches content size', async () => {
+      const w = new BrowserWindow({ show: true, width: 800, height: 600 });
+
+      await w.loadURL('about:blank');
+      expect(await getViewportSize(w)).to.deep.equal(w.getContentSize());
+    });
+  });
+
   // On Wayland, hidden windows may not have mapped surfaces or finalized geometry
   // until shown. Tests that depend on real geometry or frame events may need
   // to show the window first.