Disable tablet mode if screen reader is enabled.

This is a temporary fix while we hash out the attached a11y bugs.

Bug: 1136185, 1136236
Change-Id: I8a5ab6584fb708112c4b27ecae643be5a09f6564
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2459056Reviewed-by: Collin Baker <collinbaker@chromium.org>
Commit-Queue: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815331}

chrome/browser/ui/views/frame/browser_view.cc

@@ -172,7 +172,9 @@
 #include "content/public/common/content_switches.h"
 #include "ui/accessibility/accessibility_features.h"
 #include "ui/accessibility/ax_enums.mojom.h"
+#include "ui/accessibility/ax_mode_observer.h"
 #include "ui/accessibility/ax_node_data.h"
+#include "ui/accessibility/platform/ax_platform_node.h"
 #include "ui/base/accelerators/accelerator.h"
 #include "ui/base/dragdrop/os_exchange_data.h"
 #include "ui/base/hit_test.h"
@@ -511,6 +513,32 @@ class BrowserViewLayoutDelegateImpl : public BrowserViewLayoutDelegate {
   BrowserView* browser_view_;
 };
 
+///////////////////////////////////////////////////////////////////////////////
+// BrowserView::AccessibilityModeObserver:
+
+class BrowserView::AccessibilityModeObserver : public ui::AXModeObserver {
+ public:
+  explicit AccessibilityModeObserver(BrowserView* browser_view)
+      : browser_view_(browser_view) {
+    ui::AXPlatformNode::AddAXModeObserver(this);
+  }
+  ~AccessibilityModeObserver() override {
+    ui::AXPlatformNode::RemoveAXModeObserver(this);
+  }
+
+ private:
+  // ui::AXModeObserver:
+  void OnAXModeAdded(ui::AXMode mode) override {
+    // This will have the effect of turning tablet mode off if a screen reader
+    // is enabled while Chrome is already open. It will not return the browser
+    // to tablet mode if the user kills their screen reader.
+    if (mode.has_mode(ui::AXMode::kScreenReader))
+      browser_view_->MaybeInitializeWebUITabStrip();
+  }
+
+  BrowserView* const browser_view_;
+};
+
 ///////////////////////////////////////////////////////////////////////////////
 // BrowserView, public:
 
@@ -518,7 +546,10 @@ class BrowserViewLayoutDelegateImpl : public BrowserViewLayoutDelegate {
 const char BrowserView::kViewClassName[] = "BrowserView";
 
 BrowserView::BrowserView(std::unique_ptr<Browser> browser)
-    : views::ClientView(nullptr, nullptr), browser_(std::move(browser)) {
+    : views::ClientView(nullptr, nullptr),
+      browser_(std::move(browser)),
+      accessibility_mode_observer_(
+          std::make_unique<AccessibilityModeObserver>(this)) {
   SetShowIcon(::ShouldShowWindowIcon(browser_.get()));
   SetHasWindowSizeControls(!chrome::IsRunningInForcedAppMode());
   SetCanResize(browser_->can_resize());

chrome/browser/ui/views/frame/browser_view.h

@@ -617,6 +617,7 @@ class BrowserView : public BrowserWindow,
   friend class TopControlsSlideControllerTest;
   FRIEND_TEST_ALL_PREFIXES(BrowserViewTest, BrowserView);
   FRIEND_TEST_ALL_PREFIXES(BrowserViewTest, AccessibleWindowTitle);
+  class AccessibilityModeObserver;
 
   // If the browser is in immersive full screen mode, it will reveal the
   // tabstrip for a short duration. This is useful for shortcuts that perform
@@ -803,6 +804,13 @@ class BrowserView : public BrowserWindow,
   // the webui based tabstrip, when applicable. see https://crbug.com/989131.
   WebUITabStripContainerView* webui_tab_strip_ = nullptr;
 
+  // Allows us to react to changes in accessibility mode.
+  // TODO(dfried): this is only used to disable WebUI tabstrip (see above) while
+  // that mode has accessibile mode issues (e.g. crbug.com/1136185,
+  // crbug.com/1136236). Having an observer object allows for the browser to
+  // change mode if it enters or leaves accessibility mode.
+  std::unique_ptr<AccessibilityModeObserver> accessibility_mode_observer_;
+
   // The Toolbar containing the navigation buttons, menus and the address bar.
   ToolbarView* toolbar_ = nullptr;
 

chrome/browser/ui/views/frame/webui_tab_strip_container_view.cc

@@ -55,6 +55,8 @@
 #include "components/feature_engagement/public/tracker.h"
 #include "content/public/browser/web_ui.h"
 #include "content/public/common/drop_data.h"
+#include "ui/accessibility/ax_mode.h"
+#include "ui/accessibility/platform/ax_platform_node.h"
 #include "ui/aura/window.h"
 #include "ui/base/clipboard/clipboard_format_type.h"
 #include "ui/base/clipboard/custom_data_helper.h"
@@ -515,6 +517,14 @@ bool WebUITabStripContainerView::SupportsTouchableTabStrip(
 
 // static
 bool WebUITabStripContainerView::UseTouchableTabStrip(const Browser* browser) {
+  // TODO(crbug.com/1136185, crbug.com/1136236): We currently do not switch to
+  // touchable tabstrip in Screen Reader mode due to the touchable tabstrip
+  // being less accessible than the traditional tabstrip.
+  if (ui::AXPlatformNode::GetAccessibilityMode().has_mode(
+          ui::AXMode::kScreenReader)) {
+    return false;
+  }
+
   // This is called at Browser start to check which mode to use. It is a
   // good place to check the feature state and set up a synthetic field
   // trial.