[Mac] Turn on Auto Layout for browser windows.

chrome/browser/ui/cocoa/browser_window_controller_unittest.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 
 #include <memory>
 
 #include "base/mac/mac_util.h"
 #import "base/mac/scoped_nsobject.h"
@@ skipping 729 matching lines @@
                     object:controller_.window];
   [partial_mock verify];
 
   [[partial_mock expect] setNeedsDisplay:YES];
   [[NSNotificationCenter defaultCenter]
       postNotificationName:NSWindowDidResignMainNotification
                     object:controller_.window];
   [partial_mock verify];
 }
 
+// Test that the window uses Auto Layout. Since frame-based layout and Auto
+// Layout behave differently in subtle ways, we shouldn't start/stop using it
+// accidentally. If we don't want Auto Layout, this test should be changed to
+// expect that chromeContentView has no constraints.
+TEST_F(BrowserWindowControllerTest, UsesAutoLayout) {
+  // If Auto Layout is on, there will at least be synthesized constraints based

[tapted, 2017/03/22 22:40:00]

nit: remove `at least`?  (or "..there will be at least one synthesized
constraint..")

[Sidney San Martín, 2017/03/22 23:29:59]

Done.

+  // on the view's frame and autoresizing mask.
+  EXPECT_NE(0u, [[[controller_ chromeContentView] constraints] count]);
+}
+
 @interface BrowserWindowControllerFakeFullscreen : BrowserWindowController {
  @private
   // We release the window ourselves, so we don't have to rely on the unittest
   // doing it for us.
   base::scoped_nsobject<NSWindow> testFullscreenWindow_;
 }
 @end
 
 class BrowserWindowFullScreenControllerTest : public CocoaProfileTest {
  public:
@@ skipping 84 matching lines @@
       [[NSWindow alloc] initWithContentRect:NSMakeRect(0,0,400,400)
                                   styleMask:NSBorderlessWindowMask
                                     backing:NSBackingStoreBuffered
                                       defer:NO]);
   [[testFullscreenWindow_ contentView] setWantsLayer:YES];
   return testFullscreenWindow_.get();
 }
 @end
 
 /* TODO(???): test other methods of BrowserWindowController */