Added a class acting as a fake caret for accessibility.

content/browser/renderer_host/legacy_render_widget_host_win.cc

Index: content/browser/renderer_host/legacy_render_widget_host_win.cc
diff --git a/content/browser/renderer_host/legacy_render_widget_host_win.cc b/content/browser/renderer_host/legacy_render_widget_host_win.cc
index 42aa43cec26fe634d972b9a1bd7a59d2a6f4b1bd..107ca0a8610ef0b2e8c32ed0429f1721493b9c70 100644
--- a/content/browser/renderer_host/legacy_render_widget_host_win.cc
+++ b/content/browser/renderer_host/legacy_render_widget_host_win.cc
@@ -15,6 +15,7 @@
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 #include "content/public/common/content_switches.h"
+#include "ui/accessibility/platform/ax_fake_caret_win.h"
 #include "ui/base/view_prop.h"
 #include "ui/base/win/internal_constants.h"
 #include "ui/base/win/window_event_target.h"
@@ -170,24 +171,39 @@ LRESULT LegacyRenderWidgetHostHWND::OnGetObject(UINT message,
     return static_cast<LRESULT>(0L);
   }
 
-  if (static_cast<DWORD>(OBJID_CLIENT) != obj_id || !host_)
+  if (!host_)
     return static_cast<LRESULT>(0L);
 
-  RenderWidgetHostImpl* rwhi = RenderWidgetHostImpl::From(
-      host_->GetRenderWidgetHost());
-  if (!rwhi)
-    return static_cast<LRESULT>(0L);
+  if (static_cast<DWORD>(OBJID_CLIENT) == obj_id) {
+    RenderWidgetHostImpl* rwhi =
+        RenderWidgetHostImpl::From(host_->GetRenderWidgetHost());
+    if (!rwhi)
+      return static_cast<LRESULT>(0L);
+
+    BrowserAccessibilityManagerWin* manager =
+        static_cast<BrowserAccessibilityManagerWin*>(
+            rwhi->GetRootBrowserAccessibilityManager());
+    if (!manager)
+      return static_cast<LRESULT>(0L);
+
+    base::win::ScopedComPtr<IAccessible> root(
+        ToBrowserAccessibilityWin(manager->GetRoot()));
+    return LresultFromObject(IID_IAccessible, w_param,
+                             static_cast<IAccessible*>(root.Detach()));
+  }
 
-  BrowserAccessibilityManagerWin* manager =
-      static_cast<BrowserAccessibilityManagerWin*>(
-          rwhi->GetRootBrowserAccessibilityManager());
-  if (!manager)
-    return static_cast<LRESULT>(0L);
+  if (static_cast<DWORD>(OBJID_CARET) == obj_id && host_->HasFocus()) {
+    // Used by some assistive software to retrieve the location of the caret.
+    ui::AXFakeCaretWin* fake_caret = ui::g_ax_fake_caret_win.Pointer();
+    DCHECK(fake_caret);
+    base::win::ScopedComPtr<IAccessible> fake_caret_accessible =
+        fake_caret->GetCaret();
+    ;
+    return LresultFromObject(IID_IAccessible, w_param,
+                             fake_caret_accessible.Detach());
+  }
 
-  base::win::ScopedComPtr<IAccessible> root(
-      ToBrowserAccessibilityWin(manager->GetRoot()));
-  return LresultFromObject(IID_IAccessible, w_param,
-      static_cast<IAccessible*>(root.Detach()));
+  return static_cast<LRESULT>(0L);
 }
 
 // We send keyboard/mouse/touch messages to the parent window via SendMessage.