Implement accessibility enhancements (issue #1217)

- Add new CefBrowserHost::SetAccessibilityState method for toggling
  accessibility state when readers are detected by the client.
- Add new CefAccessibilityHandler interface for the delivery of
  accessibility notifications to windowless (OSR) clients.
- Fix delivery of CefFocusHandler callbacks to windowless clients.
- cefclient: Add example windowless accessibility implementation on Windows and macOS.
- cefclient: Automatically detect screen readers on Windows and macOS.

libcef_dll/ctocpp/accessibility_handler_ctocpp.cc

@@ -0,0 +1,75 @@
+// Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+
+#include "libcef_dll/cpptoc/value_cpptoc.h"
+#include "libcef_dll/ctocpp/accessibility_handler_ctocpp.h"
+
+
+// VIRTUAL METHODS - Body may be edited by hand.
+
+void CefAccessibilityHandlerCToCpp::OnAccessibilityTreeChange(
+    CefRefPtr<CefValue> value) {
+  cef_accessibility_handler_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, on_accessibility_tree_change))
+    return;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Verify param: value; type: refptr_diff
+  DCHECK(value.get());
+  if (!value.get())
+    return;
+
+  // Execute
+  _struct->on_accessibility_tree_change(_struct,
+      CefValueCppToC::Wrap(value));
+}
+
+void CefAccessibilityHandlerCToCpp::OnAccessibilityLocationChange(
+    CefRefPtr<CefValue> value) {
+  cef_accessibility_handler_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, on_accessibility_location_change))
+    return;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Verify param: value; type: refptr_diff
+  DCHECK(value.get());
+  if (!value.get())
+    return;
+
+  // Execute
+  _struct->on_accessibility_location_change(_struct,
+      CefValueCppToC::Wrap(value));
+}
+
+
+// CONSTRUCTOR - Do not edit by hand.
+
+CefAccessibilityHandlerCToCpp::CefAccessibilityHandlerCToCpp() {
+}
+
+template<> cef_accessibility_handler_t* CefCToCppRefCounted<CefAccessibilityHandlerCToCpp,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::UnwrapDerived(
+    CefWrapperType type, CefAccessibilityHandler* c) {
+  NOTREACHED() << "Unexpected class type: " << type;
+  return NULL;
+}
+
+#if DCHECK_IS_ON()
+template<> base::AtomicRefCount CefCToCppRefCounted<CefAccessibilityHandlerCToCpp,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::DebugObjCt = 0;
+#endif
+
+template<> CefWrapperType CefCToCppRefCounted<CefAccessibilityHandlerCToCpp,
+    CefAccessibilityHandler, cef_accessibility_handler_t>::kWrapperType =
+    WT_ACCESSIBILITY_HANDLER;

libcef_dll/ctocpp/accessibility_handler_ctocpp.h

@@ -0,0 +1,38 @@
+// Copyright (c) 2017 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+//
+// ---------------------------------------------------------------------------
+//
+// This file was generated by the CEF translator tool. If making changes by
+// hand only do so within the body of existing method and function
+// implementations. See the translator.README.txt file in the tools directory
+// for more information.
+//
+
+#ifndef CEF_LIBCEF_DLL_CTOCPP_ACCESSIBILITY_HANDLER_CTOCPP_H_
+#define CEF_LIBCEF_DLL_CTOCPP_ACCESSIBILITY_HANDLER_CTOCPP_H_
+#pragma once
+
+#if !defined(BUILDING_CEF_SHARED)
+#error This file can be included DLL-side only
+#endif
+
+#include "include/cef_accessibility_handler.h"
+#include "include/capi/cef_accessibility_handler_capi.h"
+#include "libcef_dll/ctocpp/ctocpp_ref_counted.h"
+
+// Wrap a C structure with a C++ class.
+// This class may be instantiated and accessed DLL-side only.
+class CefAccessibilityHandlerCToCpp
+    : public CefCToCppRefCounted<CefAccessibilityHandlerCToCpp,
+        CefAccessibilityHandler, cef_accessibility_handler_t> {
+ public:
+  CefAccessibilityHandlerCToCpp();
+
+  // CefAccessibilityHandler methods.
+  void OnAccessibilityTreeChange(CefRefPtr<CefValue> value) override;
+  void OnAccessibilityLocationChange(CefRefPtr<CefValue> value) override;
+};
+
+#endif  // CEF_LIBCEF_DLL_CTOCPP_ACCESSIBILITY_HANDLER_CTOCPP_H_

libcef_dll/ctocpp/browser_host_ctocpp.cc

@@ -843,6 +843,19 @@ CefRefPtr<CefNavigationEntry> CefBrowserHostCToCpp::GetVisibleNavigationEntry(
   return CefNavigationEntryCToCpp::Wrap(_retval);
 }
 
+void CefBrowserHostCToCpp::SetAccessibilityState(
+    cef_state_t accessibility_state) {
+  cef_browser_host_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, set_accessibility_state))
+    return;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  _struct->set_accessibility_state(_struct,
+      accessibility_state);
+}
+
 
 // CONSTRUCTOR - Do not edit by hand.
 

libcef_dll/ctocpp/browser_host_ctocpp.h

@@ -103,6 +103,7 @@ class CefBrowserHostCToCpp
   void DragSourceEndedAt(int x, int y, DragOperationsMask op) OVERRIDE;
   void DragSourceSystemDragEnded() OVERRIDE;
   CefRefPtr<CefNavigationEntry> GetVisibleNavigationEntry() OVERRIDE;
+  void SetAccessibilityState(cef_state_t accessibility_state) OVERRIDE;
 };
 
 #endif  // CEF_LIBCEF_DLL_CTOCPP_BROWSER_HOST_CTOCPP_H_

libcef_dll/ctocpp/render_handler_ctocpp.cc

@@ -12,11 +12,28 @@
 
 #include "libcef_dll/cpptoc/browser_cpptoc.h"
 #include "libcef_dll/cpptoc/drag_data_cpptoc.h"
+#include "libcef_dll/ctocpp/accessibility_handler_ctocpp.h"
 #include "libcef_dll/ctocpp/render_handler_ctocpp.h"
 
 
 // VIRTUAL METHODS - Body may be edited by hand.
 
+CefRefPtr<CefAccessibilityHandler> CefRenderHandlerCToCpp::GetAccessibilityHandler(
+    ) {
+  cef_render_handler_t* _struct = GetStruct();
+  if (CEF_MEMBER_MISSING(_struct, get_accessibility_handler))
+    return NULL;
+
+  // AUTO-GENERATED CONTENT - DELETE THIS COMMENT BEFORE MODIFYING
+
+  // Execute
+  cef_accessibility_handler_t* _retval = _struct->get_accessibility_handler(
+      _struct);
+
+  // Return type: refptr_same
+  return CefAccessibilityHandlerCToCpp::Wrap(_retval);
+}
+
 bool CefRenderHandlerCToCpp::GetRootScreenRect(CefRefPtr<CefBrowser> browser,
     CefRect& rect) {
   cef_render_handler_t* _struct = GetStruct();

libcef_dll/ctocpp/render_handler_ctocpp.h

@@ -31,6 +31,7 @@ class CefRenderHandlerCToCpp
   CefRenderHandlerCToCpp();
 
   // CefRenderHandler methods.
+  CefRefPtr<CefAccessibilityHandler> GetAccessibilityHandler() override;
   bool GetRootScreenRect(CefRefPtr<CefBrowser> browser, CefRect& rect) override;
   bool GetViewRect(CefRefPtr<CefBrowser> browser, CefRect& rect) override;
   bool GetScreenPoint(CefRefPtr<CefBrowser> browser, int viewX, int viewY,