Ensure Windows accessibility is enabled properly.

http://crrev.com/c/1192062 made it so that we don't enable accessibility
as often. The idea was to only enable accessibility if we get a call to
IAccessible2, or to both get_accName and a response to our alert message
on a honeypot window.

However, this only worked if we constructed at least one
BrowserAccessibilityManager. In cases where the external client
never explored and discovered a BrowserAccessibilityManager, the
IAccessible2UsageObserver wasn't registered yet.

As a fix, move the IAccessible2UsageObserver code to part of
BrowserAccessibilityStateImpl.

Bug: 878072
Change-Id: Iadcbd032fa1d6f635bbb99c1e130d384efe0d9b1
Reviewed-on: https://chromium-review.googlesource.com/1234267Reviewed-by: Aaron Leventhal <aleventhal@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593233}

content/browser/accessibility/browser_accessibility_manager_win.cc

@@ -19,10 +19,6 @@
 
 namespace content {
 
-// See OnScreenReaderHoneyPotQueried, below.
-bool g_screen_reader_honeypot_queried = false;
-bool g_acc_name_called = false;
-
 // static
 BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
     const ui::AXTreeUpdate& initial_tree,
@@ -44,7 +40,6 @@ BrowserAccessibilityManagerWin::BrowserAccessibilityManagerWin(
       load_complete_pending_(false) {
   ui::win::CreateATLModuleIfNeeded();
   Initialize(initial_tree);
-  ui::GetIAccessible2UsageObserverList().AddObserver(this);
 }
 
 BrowserAccessibilityManagerWin::~BrowserAccessibilityManagerWin() {
@@ -52,7 +47,6 @@ BrowserAccessibilityManagerWin::~BrowserAccessibilityManagerWin() {
   // destructor, otherwise our overrides of functions like
   // OnNodeWillBeDeleted won't be called.
   tree_.reset(NULL);
-  ui::GetIAccessible2UsageObserverList().RemoveObserver(this);
 }
 
 // static
@@ -76,38 +70,6 @@ HWND BrowserAccessibilityManagerWin::GetParentHWND() {
   return delegate->AccessibilityGetAcceleratedWidget();
 }
 
-void BrowserAccessibilityManagerWin::OnIAccessible2Used() {
-  // When IAccessible2 APIs have been used elsewhere in the codebase,
-  // enable basic web accessibility support. (Full screen reader support is
-  // detected later when specific more advanced APIs are accessed.)
-  BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
-      ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
-}
-
-void BrowserAccessibilityManagerWin::OnScreenReaderHoneyPotQueried() {
-  // We used to trust this as a signal that a screen reader is running,
-  // but it's been abused. Now only enable accessibility if we also
-  // detect a call to get_accName.
-  if (g_screen_reader_honeypot_queried)
-    return;
-  g_screen_reader_honeypot_queried = true;
-  if (g_acc_name_called) {
-    BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
-        ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
-  }
-}
-
-void BrowserAccessibilityManagerWin::OnAccNameCalled() {
-  // See OnScreenReaderHoneyPotQueried, above.
-  if (g_acc_name_called)
-    return;
-  g_acc_name_called = true;
-  if (g_screen_reader_honeypot_queried) {
-    BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
-        ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
-  }
-}
-
 void BrowserAccessibilityManagerWin::UserIsReloading() {
   if (GetRoot())
     FireWinAccessibilityEvent(IA2_EVENT_DOCUMENT_RELOAD, GetRoot());

content/browser/accessibility/browser_accessibility_manager_win.h

@@ -18,8 +18,7 @@ class BrowserAccessibilityWin;
 
 // Manages a tree of BrowserAccessibilityWin objects.
 class CONTENT_EXPORT BrowserAccessibilityManagerWin
-    : public BrowserAccessibilityManager,
-      public ui::IAccessible2UsageObserver {
+    : public BrowserAccessibilityManager {
  public:
   BrowserAccessibilityManagerWin(
       const ui::AXTreeUpdate& initial_tree,
@@ -33,11 +32,6 @@ class CONTENT_EXPORT BrowserAccessibilityManagerWin
   // Get the closest containing HWND.
   HWND GetParentHWND();
 
-  // IAccessible2UsageObserver
-  void OnIAccessible2Used() override;
-  void OnScreenReaderHoneyPotQueried() override;
-  void OnAccNameCalled() override;
-
   // BrowserAccessibilityManager methods
   void UserIsReloading() override;
   BrowserAccessibility* GetFocus() override;

content/browser/accessibility/browser_accessibility_state_impl.cc

@@ -168,6 +168,8 @@ ui::AXMode BrowserAccessibilityStateImpl::GetAccessibilityMode() const {
 }
 
 #if !defined(OS_WIN) && !defined(OS_MACOSX)
+void BrowserAccessibilityStateImpl::PlatformInitialize() {}
+
 void BrowserAccessibilityStateImpl::UpdatePlatformSpecificHistograms() {
 }
 #endif

content/browser/accessibility/browser_accessibility_state_impl.h

@@ -84,6 +84,7 @@ class CONTENT_EXPORT BrowserAccessibilityStateImpl
   // Leaky singleton, destructor generally won't be called.
   ~BrowserAccessibilityStateImpl() override;
 
+  void PlatformInitialize();
   void UpdatePlatformSpecificHistograms();
 
   ui::AXMode accessibility_mode_;

content/browser/accessibility/browser_accessibility_state_impl_mac.mm

@@ -18,6 +18,8 @@
 
 namespace content {
 
+void BrowserAccessibilityStateImpl::PlatformInitialize() {}
+
 void BrowserAccessibilityStateImpl::UpdatePlatformSpecificHistograms() {
   // NOTE: This function is running on the file thread.
   NSWorkspace* workspace = [NSWorkspace sharedWorkspace];

content/browser/accessibility/browser_accessibility_state_impl_win.cc

@@ -15,9 +15,65 @@
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_util.h"
+#include "ui/accessibility/platform/ax_platform_node_win.h"
 
 namespace content {
 
+namespace {
+
+// Enables accessibility based on three possible clues that indicate
+// accessibility API usage.
+//
+// TODO(dmazzoni): Rename IAccessible2UsageObserver to something more general.
+class WindowsAccessibilityEnabler : public ui::IAccessible2UsageObserver {
+ public:
+  WindowsAccessibilityEnabler() {}
+
+ private:
+  // IAccessible2UsageObserver
+  void OnIAccessible2Used() override {
+    // When IAccessible2 APIs have been used elsewhere in the codebase,
+    // enable basic web accessibility support. (Full screen reader support is
+    // detected later when specific more advanced APIs are accessed.)
+    BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
+        ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
+  }
+
+  void OnScreenReaderHoneyPotQueried() override {
+    // We used to trust this as a signal that a screen reader is running,
+    // but it's been abused. Now only enable accessibility if we also
+    // detect a call to get_accName.
+    if (screen_reader_honeypot_queried_)
+      return;
+    screen_reader_honeypot_queried_ = true;
+    if (acc_name_called_) {
+      BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
+          ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
+    }
+  }
+
+  void OnAccNameCalled() override {
+    // See OnScreenReaderHoneyPotQueried, above.
+    if (acc_name_called_)
+      return;
+    acc_name_called_ = true;
+    if (screen_reader_honeypot_queried_) {
+      BrowserAccessibilityStateImpl::GetInstance()->AddAccessibilityModeFlags(
+          ui::AXMode::kNativeAPIs | ui::AXMode::kWebContents);
+    }
+  }
+
+  bool screen_reader_honeypot_queried_ = false;
+  bool acc_name_called_ = false;
+};
+
+}  // namespace
+
+void BrowserAccessibilityStateImpl::PlatformInitialize() {
+  ui::GetIAccessible2UsageObserverList().AddObserver(
+      new WindowsAccessibilityEnabler());
+}
+
 void BrowserAccessibilityStateImpl::UpdatePlatformSpecificHistograms() {
   // NOTE: this method is run from the file thread to reduce jank, since
   // there's no guarantee these system calls will return quickly. Be careful