Revert: Free up accessibility tree resources from hidden frames.

It was causing too many problems like being unable to inspect background
tabs in chrome://accessibility and losing your place when switching tabs.
We should come up with a better fix.

Original change: crrev.com/c/1107207

TBR=nektar@chromium.org

Bug: 854411, 856163, 856160
Change-Id: Iaef9b8ccbd47defba02e4e887f8219d00e77a808
Reviewed-on: https://chromium-review.googlesource.com/1131846Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573876}

chrome/test/data/extensions/api_test/automation/tests/tabs/tab_id.js

+
 // Copyright 2014 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.
 
-function createTabInNewInactiveWindow(url, callback) {
+function createBackgroundTab(url, callback) {
   chrome.tabs.query({ active: true }, function(tabs) {
     chrome.test.assertEq(1, tabs.length);
     var originalActiveTab = tabs[0];
-    chrome.windows.create({"url": url, "focused": false}, function(win) {
+    createTab(url, function(tab) {
       chrome.tabs.update(originalActiveTab.id, { active: true }, function() {
-        callback(win.tabs[0]);
+        callback(tab);
       });
     })
   });
@@ -25,7 +26,7 @@ var allTests = [
     getUrlFromConfig('index.html', function(url) {
       // Keep the NTP as the active tab so that we know we're requesting the
       // tab by ID rather than just getting the active tab still.
-      createTabInNewInactiveWindow(url, function(tab) {
+      createBackgroundTab(url, function(tab) {
         chrome.automation.getTree(tab.id, function(rootNode) {
           if (rootNode.docLoaded) {
             assertCorrectTab(rootNode);

content/renderer/accessibility/blink_ax_tree_source.cc

@@ -215,22 +215,11 @@ ScopedFreezeBlinkAXTreeSource::~ScopedFreezeBlinkAXTreeSource() {
 
 BlinkAXTreeSource::BlinkAXTreeSource(RenderFrameImpl* render_frame,
                                      ui::AXMode mode)
-    : render_frame_(render_frame),
-      accessibility_mode_(mode),
-      frozen_(false),
-      hidden_(false) {}
+    : render_frame_(render_frame), accessibility_mode_(mode), frozen_(false) {}
 
 BlinkAXTreeSource::~BlinkAXTreeSource() {
 }
 
-void BlinkAXTreeSource::WasHidden() {
-  hidden_ = true;
-}
-
-void BlinkAXTreeSource::WasShown() {
-  hidden_ = false;
-}
-
 void BlinkAXTreeSource::Freeze() {
   CHECK(!frozen_);
   frozen_ = true;
@@ -384,9 +373,6 @@ void BlinkAXTreeSource::GetChildren(
     std::vector<WebAXObject>* out_children) const {
   CHECK(frozen_);
 
-  if (hidden_)
-    return;
-
   if ((parent.Role() == blink::kWebAXRoleStaticText ||
        parent.Role() == blink::kWebAXRoleLineBreak) &&
       ShouldLoadInlineTextBoxes(parent)) {
@@ -424,9 +410,6 @@ void BlinkAXTreeSource::GetChildren(
 WebAXObject BlinkAXTreeSource::GetParent(WebAXObject node) const {
   CHECK(frozen_);
 
-  if (hidden_)
-    return WebAXObject();
-
   // Blink returns ignored objects when walking up the parent chain,
   // we have to skip those here. Also, stop when we get to the root
   // element.
@@ -440,9 +423,6 @@ WebAXObject BlinkAXTreeSource::GetParent(WebAXObject node) const {
 }
 
 bool BlinkAXTreeSource::IsValid(WebAXObject node) const {
-  if (hidden_ && !node.Equals(root()))
-    return false;
-
   return !node.IsDetached();  // This also checks if it's null.
 }
 

content/renderer/accessibility/blink_ax_tree_source.h

@@ -42,11 +42,6 @@ class BlinkAXTreeSource
   BlinkAXTreeSource(RenderFrameImpl* render_frame, ui::AXMode mode);
   ~BlinkAXTreeSource() override;
 
-  // If the frame is hidden, expose only the root node and skip the
-  // rest of the tree.
-  void WasHidden();
-  void WasShown();
-
   // Freeze caches the document, accessibility root, and current focused
   // object for fast retrieval during a batch of operations. Use
   // ScopedFreezeBlinkAXTreeSource on the stack rather than calling
@@ -140,10 +135,6 @@ class BlinkAXTreeSource
   blink::WebDocument document_;
   blink::WebAXObject root_;
   blink::WebAXObject focus_;
-
-  // If the page is hidden, we eliminate everything other than the
-  // root node.
-  bool hidden_;
 };
 
 }  // namespace content

content/renderer/accessibility/render_accessibility_impl.cc

@@ -125,9 +125,6 @@ RenderAccessibilityImpl::RenderAccessibilityImpl(RenderFrameImpl* render_frame,
     settings->SetInlineTextBoxAccessibilityEnabled(true);
 #endif
 
-  if (render_frame_->IsHidden())
-    tree_source_.WasHidden();
-
   const WebDocument& document = GetMainDocument();
   if (!document.IsNull()) {
     // It's possible that the webview has already loaded a webpage without
@@ -197,22 +194,8 @@ bool RenderAccessibilityImpl::OnMessageReceived(const IPC::Message& message) {
   return handled;
 }
 
-void RenderAccessibilityImpl::WasHidden() {
-  pending_events_.clear();
-  tree_source_.WasHidden();
-  HandleAXEvent(tree_source_.GetRoot(), ax::mojom::Event::kNone);
-}
-
-void RenderAccessibilityImpl::WasShown() {
-  pending_events_.clear();
-  tree_source_.WasShown();
-  HandleAXEvent(tree_source_.GetRoot(), ax::mojom::Event::kNone);
-}
-
 void RenderAccessibilityImpl::HandleWebAccessibilityEvent(
     const blink::WebAXObject& obj, blink::WebAXEvent event) {
-  if (render_frame_->IsHidden())
-    return;
   HandleAXEvent(obj, AXEventFromBlink(event));
 }
 

content/renderer/accessibility/render_accessibility_impl.h

@@ -75,8 +75,6 @@ class CONTENT_EXPORT RenderAccessibilityImpl
   // RenderFrameObserver implementation.
   void AccessibilityModeChanged() override;
   bool OnMessageReceived(const IPC::Message& message) override;
-  void WasHidden() override;
-  void WasShown() override;
 
   // Called when an accessibility notification occurs in Blink.
   void HandleWebAccessibilityEvent(const blink::WebAXObject& obj,