DialogBrowserTest support pixel tests

With this change, all DialogBrowserTest should be abled to verify pixel correctness.
To use them as pixel test, add flag --browser-ui-tests-verify-pixels.
TEST: browser_tests.exe --gtest_filter=PermissionDialogTest.*
--browser-ui-tests-verify-pixels --enable-pixel-output-in-tests
--build-revision=b6aaf42b --no-luci-auth
I've approved the following images so these tests can pass now.
https://chrome-gpu-gold.skia.org/detail?test=BrowserUiDialog_PermissionDialogTest_InvokeUi_protocol_handlers&digest=877f6df6101e926f24c5b9bc3cf111b3
https://chrome-gpu-gold.skia.org/detail?test=BrowserUiDialog_PermissionDialogTest_InvokeUi_camera&digest=cf09792802b243e0a33bf4d45e2e8047
I didn't start with test_browser_ui because most of the tests are inherited from test_browser_dialog.

Next step:
1 Add some tests to fyi bots to monitor the stability.
2 Fix some tests that don't have stable UI. Eg disable animation for
https://chrome-gpu-gold.skia.org/detail?test=BrowserUiDialog_AuthenticatorDialogViewTest_InvokeUi_default&digest=2442c011949e9f98f4442f066bb90e55

Bug: 958242
Change-Id: I7bc048b792a5e303e8ee948fda228fa664395ca1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1756604
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688211}

chrome/browser/ui/test/test_browser_dialog.cc

@@ -10,6 +10,7 @@
 #include "base/stl_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
+#include "chrome/test/pixel/browser_skia_gold_pixel_diff.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 #if defined(OS_CHROMEOS)
@@ -21,6 +22,7 @@
 #endif
 
 #if defined(TOOLKIT_VIEWS)
+#include "base/strings/strcat.h"
 #include "ui/display/display.h"
 #include "ui/display/screen.h"
 #include "ui/views/test/widget_test.h"
@@ -53,17 +55,43 @@ class WidgetCloser {
 
   DISALLOW_COPY_AND_ASSIGN(WidgetCloser);
 };
+
+class CompositorObserverEnd : public ui::CompositorObserver {
+ public:
+  void OnCompositingEnded(ui::Compositor* compositor) override {
+    base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE,
+                                                  run_loop_.QuitClosure());
+  }
+  void WaitForComplete() { run_loop_.Run(); }
+
+ private:
+  base::RunLoop run_loop_;
+};
+
 #endif  // defined(TOOLKIT_VIEWS)
 
 }  // namespace
 
-TestBrowserDialog::TestBrowserDialog() = default;
+TestBrowserDialog::TestBrowserDialog() : TestBrowserUi() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          "browser-ui-tests-verify-pixels")) {
+    pixel_diff_ = std::make_unique<BrowserSkiaGoldPixelDiff>();
+  }
+}
+
 TestBrowserDialog::~TestBrowserDialog() = default;
 
 void TestBrowserDialog::PreShow() {
   UpdateWidgets();
 }
 
+void CompareAsync(const BrowserSkiaGoldPixelDiff* pixel_diff,
+                  const std::string& name,
+                  const views::View* view,
+                  bool* result) {
+  *result = pixel_diff->CompareScreenshot(name, view);
+}
+
 // This returns true if exactly one views widget was shown that is a dialog or
 // has a name matching the test-specified name, and if that window is in the
 // work area (if |should_verify_dialog_bounds_| is true).
@@ -87,13 +115,41 @@ bool TestBrowserDialog::VerifyUi() {
   if (added.size() != 1)
     return false;
 
+  views::Widget* dialog_widget = *(added.begin());
+// TODO(https://crbug.com/958242) support Mac for pixel tests.
+#if !defined(OS_MACOSX)
+  if (pixel_diff_) {
+    // Wait for painting complete.
+    auto* compositor = dialog_widget->GetNativeView()->layer()->GetCompositor();
+    CompositorObserverEnd obend;
+    compositor->AddObserver(&obend);
+    obend.WaitForComplete();
+    compositor->RemoveObserver(&obend);
+
+    base::ScopedAllowBlockingForTesting allow_blocking;
+    pixel_diff_->Init(dialog_widget, "BrowserUiDialog");
+    auto* test_info = testing::UnitTest::GetInstance()->current_test_info();
+    const std::string test_name =
+        base::StrCat({test_info->test_case_name(), "_", test_info->name()});
+    bool result = false;
+    base::RunLoop run_loop;
+    base::ThreadTaskRunnerHandle::Get()->PostTaskAndReply(
+        FROM_HERE,
+        base::BindOnce(CompareAsync, pixel_diff_.get(), test_name,
+                       dialog_widget->GetContentsView(), &result),
+        run_loop.QuitClosure());
+    run_loop.Run();
+    if (!result)
+      return false;
+  }
+#endif  // OS_MACOSX
+
   if (!should_verify_dialog_bounds_)
     return true;
 
   // Verify that the dialog's dimensions do not exceed the display's work area
   // bounds, which may be smaller than its bounds(), e.g. in the case of the
   // docked magnifier or Chromevox being enabled.
-  views::Widget* dialog_widget = *(added.begin());
   const gfx::Rect dialog_bounds = dialog_widget->GetWindowBoundsInScreen();
   gfx::NativeWindow native_window = dialog_widget->GetNativeWindow();
   DCHECK(native_window);

chrome/browser/ui/test/test_browser_dialog.h

@@ -13,6 +13,8 @@
 #include "ui/views/widget/widget.h"
 #endif
 
+class BrowserSkiaGoldPixelDiff;
+
 // A dialog-specific subclass of TestBrowserUi, which will verify that a test
 // showed a single dialog.
 class TestBrowserDialog : public TestBrowserUi {
@@ -55,6 +57,9 @@ class TestBrowserDialog : public TestBrowserUi {
   // This should always be true, but some dialogs don't yet size themselves
   // properly. https://crbug.com/893292.
   bool should_verify_dialog_bounds_ = true;
+  // If this variable is set, VerifyUi will verify pixel correctness for
+  // the dialog.
+  std::unique_ptr<BrowserSkiaGoldPixelDiff> pixel_diff_;
 
   DISALLOW_COPY_AND_ASSIGN(TestBrowserDialog);
 };

chrome/test/pixel/browser_skia_gold_pixel_diff.h

@@ -25,7 +25,7 @@ class Image;
 class BrowserSkiaGoldPixelDiff : public SkiaGoldPixelDiff {
  public:
   BrowserSkiaGoldPixelDiff();
-  ~BrowserSkiaGoldPixelDiff();
+  ~BrowserSkiaGoldPixelDiff() override;
   // Call Init method before using this class.
   // Args:
   // widget The instance you plan to take screenshots with.

ui/base/test/skia_gold_pixel_diff.h

@@ -19,7 +19,7 @@ class SkBitmap;
 class SkiaGoldPixelDiff {
  public:
   SkiaGoldPixelDiff();
-  ~SkiaGoldPixelDiff();
+  virtual ~SkiaGoldPixelDiff();
   // Call Init method before using this class.
   // Args:
   // screenshot_prefix The prefix for your screenshot name on GCS.