Add a WebContentsImpl API to snapshot the accessibility tree.

content/browser/accessibility/snapshot_ax_tree_browsertest.cc

+// Copyright 2015 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.
+
+#include "base/callback.h"
+#include "content/browser/web_contents/web_contents_impl.h"
+#include "content/public/test/content_browser_test.h"
+#include "content/public/test/content_browser_test_utils.h"
+#include "content/public/test/test_utils.h"
+#include "content/shell/browser/shell.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "ui/accessibility/ax_node.h"
+#include "ui/accessibility/ax_tree.h"
+
+namespace content {
+
+namespace {
+
+class AXTreeSnapshotWaiter {
+ public:
+  AXTreeSnapshotWaiter() : loop_runner_(new MessageLoopRunner()) {}
+
+  void Wait() {
+    loop_runner_->Run();
+  }
+
+  const ui::AXTreeUpdate& snapshot() const { return snapshot_; }
+
+  void ReceiveSnapshot(const ui::AXTreeUpdate& snapshot) {
+    snapshot_ = snapshot;
+    loop_runner_->Quit();
+  }
+
+ private:
+  ui::AXTreeUpdate snapshot_;
+  scoped_refptr<MessageLoopRunner> loop_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(AXTreeSnapshotWaiter);
+};
+
+}  // namespace
+
+class SnapshotAXTreeBrowserTest : public ContentBrowserTest {
+ public:
+  SnapshotAXTreeBrowserTest() {}
+  ~SnapshotAXTreeBrowserTest() override {}
+};
+
+IN_PROC_BROWSER_TEST_F(SnapshotAXTreeBrowserTest,
+                       SnapshotAccessibilityTreeFromWebContents) {
+  GURL url("data:text/html,<button>Click</button>");
+  NavigateToURL(shell(), url);
+
+  WebContentsImpl* web_contents =
+      static_cast<WebContentsImpl*>(shell()->web_contents());
+
+  AXTreeSnapshotWaiter waiter;
+  web_contents->RequestAXTreeSnapshot(
+      base::Bind(&AXTreeSnapshotWaiter::ReceiveSnapshot,
+                 base::Unretained(&waiter)));
+  waiter.Wait();
+
+  // Dump the whole tree if one of the assertions below fails
+  // to aid in debugging why it failed.
+  SCOPED_TRACE(waiter.snapshot().ToString());
+
+  ui::AXTree tree(waiter.snapshot());
+  ui::AXNode* root = tree.root();
+  ASSERT_NE(nullptr, root);
+  ASSERT_EQ(ui::AX_ROLE_ROOT_WEB_AREA, root->data().role);
+  ui::AXNode* group = root->ChildAtIndex(0);
+  ASSERT_EQ(ui::AX_ROLE_GROUP, group->data().role);
+  ui::AXNode* button = group->ChildAtIndex(0);
+  ASSERT_EQ(ui::AX_ROLE_BUTTON, button->data().role);
+}
+
+}  // namespace content