Reland "Enable the pixel by pixel comparison test for Mac OS."

This is a reland of 01ccf727

Original change's description:
> Enable the pixel by pixel comparison test for Mac OS.
> 
> 1. Tested on Mac and verify everything works as expected.
> 2. Removed the unnecessary call of GetNativeWindow().
> 
> Change-Id: I377e6bfb004548887b9623b0094da91fa36b4d1c
> Reviewed-on: https://chromium-review.googlesource.com/c/1279301
> Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
> Commit-Queue: Clifford Cheng <cliffordcheng@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#601879}

Change-Id: Ib6fa1c1d9b3487c88b240ea9262042db8af0c19a
Reviewed-on: https://chromium-review.googlesource.com/c/1296811Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: Clifford Cheng <cliffordcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603544}

chrome/browser/picture_in_picture/picture_in_picture_window_controller_browsertest.cc

@@ -12,7 +12,6 @@
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
-#include "chrome/browser/ui/views/overlay/overlay_window_views.h"
 #include "chrome/test/base/in_process_browser_test.h"
 #include "chrome/test/base/ui_test_utils.h"
 #include "components/viz/common/frame_sinks/copy_output_request.h"
@@ -190,7 +189,7 @@ IN_PROC_BROWSER_TEST_F(PictureInPictureWindowControllerBrowserTest,
   EXPECT_TRUE(window_controller()->GetWindowForTesting()->IsVisible());
 }
 
-#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
+#if (defined(OS_MACOSX) || defined(OS_LINUX)) && !defined(OS_CHROMEOS)
 class PictureInPicturePixelComparisonBrowserTest
     : public PictureInPictureWindowControllerBrowserTest {
  public:
@@ -233,8 +232,7 @@ class PictureInPicturePixelComparisonBrowserTest
             base::BindOnce(
                 &PictureInPicturePixelComparisonBrowserTest::ReadbackResult,
                 base::Unretained(this), run_loop.QuitClosure()));
-    overlay_window_views->GetNativeWindow()->layer()->RequestCopyOfOutput(
-        std::move(request));
+    overlay_window_views->GetLayer()->RequestCopyOfOutput(std::move(request));
     run_loop.Run();
   }
 
@@ -271,8 +269,7 @@ class PictureInPicturePixelComparisonBrowserTest
   std::unique_ptr<SkBitmap> result_bitmap_;
 };
 
-// TODO(cliffordcheng): enable this tests on other platforms when
-// Windows and Mac capture screen problem is solved.
+// TODO(cliffordcheng): enable on Windows when compile errors are resolved.
 // Plays a video and then trigger Picture-in-Picture. Grabs a screenshot of
 // Picture-in-Picture window and verifies it's as expected.
 IN_PROC_BROWSER_TEST_F(PictureInPicturePixelComparisonBrowserTest, VideoPlay) {
@@ -320,7 +317,7 @@ IN_PROC_BROWSER_TEST_F(PictureInPicturePixelComparisonBrowserTest, VideoPlay) {
   ASSERT_TRUE(SaveBitmap(test_image_path, GetResultBitmap()));
   EXPECT_TRUE(CompareImages(GetResultBitmap()));
 }
-#endif  // defined(OS_LINUX) && !defined(OS_CHROMEOS)
+#endif  // (defined(OS_MACOSX) || defined(OS_LINUX)) && !defined(OS_CHROMEOS)
 
 // Tests that when an active WebContents accurately tracks whether a video
 // is in Picture-in-Picture.