Re-land: Fix loading accessibility tree for child frame that's already loaded.

content/browser/accessibility/dump_accessibility_browsertest_base.cc

Index: content/browser/accessibility/dump_accessibility_browsertest_base.cc
diff --git a/content/browser/accessibility/dump_accessibility_browsertest_base.cc b/content/browser/accessibility/dump_accessibility_browsertest_base.cc
index af1e10e1d7863fb022ca4133e63638c851e9d739..117913fbda471ba393891a2b3d598d98129350fb 100644
--- a/content/browser/accessibility/dump_accessibility_browsertest_base.cc
+++ b/content/browser/accessibility/dump_accessibility_browsertest_base.cc
@@ -75,7 +75,9 @@ bool AccessibilityTreeContainsLoadedDocWithUrl(BrowserAccessibility* node,
 
 typedef AccessibilityTreeFormatter::Filter Filter;
 
-DumpAccessibilityTestBase::DumpAccessibilityTestBase() {
+DumpAccessibilityTestBase::DumpAccessibilityTestBase()
+    : is_blink_pass_(false),
+      enable_accessibility_after_navigating_(false) {
 }
 
 DumpAccessibilityTestBase::~DumpAccessibilityTestBase() {
@@ -245,15 +247,31 @@ void DumpAccessibilityTestBase::RunTestForPlatform(
   AddDefaultFilters(&filters_);
   ParseHtmlForExtraDirectives(html_contents, &filters_, &wait_for);
 
-  // Load the test html and wait for the "load complete" AX event.
+  // Get the test URL.
   GURL url(embedded_test_server()->GetURL(
       "/" + std::string(file_dir) + "/" + file_path.BaseName().MaybeAsASCII()));
-  AccessibilityNotificationWaiter accessibility_waiter(
-      shell()->web_contents(),
-      AccessibilityModeComplete,
-      ui::AX_EVENT_LOAD_COMPLETE);
-  NavigateToURL(shell(), url);
-  accessibility_waiter.WaitForNotification();
+
+  // Make sure accessibility is off initially.
+  BrowserAccessibilityStateImpl::GetInstance()->DisableAccessibility();
+
+  if (enable_accessibility_after_navigating_) {
+    // Load the url, then enable accessibility.
+    NavigateToURL(shell(), url);
+    AccessibilityNotificationWaiter accessibility_waiter(
+        shell()->web_contents(),
+        AccessibilityModeComplete,
+        ui::AX_EVENT_NONE);
+    accessibility_waiter.WaitForNotification();
+  } else {
+    // Enable accessibility, then load the test html and wait for the
+    // "load complete" AX event.
+    AccessibilityNotificationWaiter accessibility_waiter(
+        shell()->web_contents(),
+        AccessibilityModeComplete,
+        ui::AX_EVENT_LOAD_COMPLETE);
+    NavigateToURL(shell(), url);
+    accessibility_waiter.WaitForNotification();
+  }
 
   // Get the url of every frame in the frame tree.
   WebContentsImpl* web_contents = static_cast<WebContentsImpl*>(