Add a TestBrowserDialog helper class for testing browser dialogs in a consistent way.

chrome/browser/ui/test/test_browser_dialog.h

Index: chrome/browser/ui/test/test_browser_dialog.h
diff --git a/chrome/browser/ui/test/test_browser_dialog.h b/chrome/browser/ui/test/test_browser_dialog.h
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+// Copyright 2016 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.
+
+#ifndef CHROME_BROWSER_UI_TEST_TEST_BROWSER_DIALOG_H_
+#define CHROME_BROWSER_UI_TEST_TEST_BROWSER_DIALOG_H_
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "chrome/browser/ui/browser_window.h"
+#include "chrome/test/base/in_process_browser_test.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/gfx/native_widget_types.h"
+
+// TestBrowserDialog provides a way to register an InProcessBrowserTest testing
+// harness with a framework that invokes Chrome browser dialogs in a consistent
+// way. It optionally provides a way to invoke dialogs "interactively". This
+// allows screenshots to be generated easily, with the same test data, to assist
+// with UI review. It also provides a registry of dialogs so they can be
+// systematically checked for subtle changes and regressions.
+//
+// To use TestBrowserDialog, a test harness should inherit from
+// DialogBrowserTest rather than InProcessBrowserTest. If the dialog under test
+// has only a single mode of operation, the only other requirement on the test
+// harness is an override:
+//
+// class FooDialogTest : public DialogBrowserTest {
+//  public:
+//   ..
+//   // DialogBrowserTest:
+//   void ShowDialog(const std::string& name) override {
+//     /* Show dialog attached to browser() and leave it open. */
+//   }
+//   ..
+// };
+//
+// then in the foo_dialog_browsertest.cc, define any number of
+//
+// IN_PROC_BROWSER_TEST_F(FooDialogTest, InvokeDialog_name) {
+//   RunDialog();
+// }
+//
+// The string after "InvokeDialog_" (here, "name") is the argument given to
+// ShowDialog(). In a regular test suite run, RunDialog() shows the dialog and
+// immediately closes it (after ensuring it was actually created).
+//
+// To get a list of all available dialogs, run the `BrowserDialogTest.Invoke`
+// test case without other arguments. I.e.
+//
+//   browser_tests --gtest_filter=BrowserDialogTest.Invoke
+//
+// Dialogs listed can be shown interactively using the --dialog argument. E.g.
+//
+//   browser_tests --gtest_filter=BrowserDialogTest.Invoke --interactive \
+//       --dialog=FooDialogTest.InvokeDialog_name
+class TestBrowserDialog {
+ protected:
+  TestBrowserDialog();
+
+  // Runs the dialog whose name corresponds to the current test case.
+  void RunDialog();
+
+  // Show the dialog corresponding to |name| and leave it open.
+  virtual void ShowDialog(const std::string& name) = 0;
+
+  // The window that owns the dialogs. Used to find where the dialog appears.
+  virtual gfx::NativeWindow DialogParent() = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TestBrowserDialog);
+};
+
+// Helper to mix in a TestBrowserDialog to an existing test harness. |Base|
+// must be a descendant of InProcessBrowserTest.
+template <class Base>
+class SupportsTestDialog : public Base, public TestBrowserDialog {
+ protected:
+  SupportsTestDialog() {}
+
+  // TestBrowserDialog:
+  gfx::NativeWindow DialogParent() override {
+    return this->browser()->window()->GetNativeWindow();
+  }
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(SupportsTestDialog);
+};
+
+using DialogBrowserTest = SupportsTestDialog<InProcessBrowserTest>;
+
+namespace internal {
+
+// When present on the command line, runs the test in an interactive mode.
+constexpr const char kInteractiveSwitch[] = "interactive";
+
+}  // namespace internal
+
+#endif  // CHROME_BROWSER_UI_TEST_TEST_BROWSER_DIALOG_H_