Added a class acting as a fake caret for accessibility.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 61b60b05345b9f7bc3b334c2517a143d09559918..8696db3db8ae30348842429e2c8b01c331c7906b 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -103,6 +103,7 @@
 #include "content/browser/accessibility/browser_accessibility_manager_win.h"
 #include "content/browser/accessibility/browser_accessibility_win.h"
 #include "content/browser/renderer_host/legacy_render_widget_host_win.h"
+#include "ui/accessibility/platform/ax_fake_caret_win.h"
 #include "ui/base/win/hidden_window.h"
 #include "ui/base/win/osk_display_manager.h"
 #include "ui/base/win/osk_display_observer.h"
@@ -885,7 +886,9 @@ void RenderWidgetHostViewAura::UpdateMouseLockRegion() {
 }
 
 void RenderWidgetHostViewAura::OnLegacyWindowDestroyed() {
-  legacy_render_widget_host_HWND_ = NULL;
+  ui::AXFakeCaretWin::Get()->SetTargetForNativeAccessibilityEvent(

[dmazzoni, 2017/04/21 21:06:30]

Hmmm, I wonder if it'd make more sense for each
HWND to just own its own instance of AXFakeCaretWin,
then you wouldn't need to do any of this. What do
you think?

+      gfx::kNullAcceleratedWidget);
+  legacy_render_widget_host_HWND_ = nullptr;
   legacy_window_destroyed_ = true;
 }
 #endif
@@ -1556,6 +1559,8 @@ void RenderWidgetHostViewAura::OnWindowDestroying(aura::Window* window) {
     // The Destroy call above will delete the LegacyRenderWidgetHostHWND
     // instance.
     legacy_render_widget_host_HWND_ = NULL;
+    ui::AXFakeCaretWin::Get()->SetTargetForNativeAccessibilityEvent(
+        gfx::kNullAcceleratedWidget);
   }
 #endif
 
@@ -2155,6 +2160,8 @@ void RenderWidgetHostViewAura::UpdateLegacyWin() {
     // here.
     if (!host_->is_hidden())
       legacy_render_widget_host_HWND_->Show();
+    ui::AXFakeCaretWin::Get()->SetTargetForNativeAccessibilityEvent(
+        legacy_render_widget_host_HWND_->hwnd());
   }
 }
 #endif
@@ -2333,7 +2340,6 @@ void RenderWidgetHostViewAura::OnSelectionBoundsChanged(
 void RenderWidgetHostViewAura::OnTextSelectionChanged(
     TextInputManager* text_input_manager,
     RenderWidgetHostViewBase* updated_view) {
-#if defined(USE_X11) && !defined(OS_CHROMEOS)
   if (!GetTextInputManager())
     return;
 
@@ -2350,6 +2356,7 @@ void RenderWidgetHostViewAura::OnTextSelectionChanged(
   if (!focused_view)
     return;
 
+#if defined(USE_X11) && !defined(OS_CHROMEOS)
   const TextInputManager::TextSelection* selection =
       GetTextInputManager()->GetTextSelection(focused_view);
   if (selection->selected_text().length()) {
@@ -2357,7 +2364,24 @@ void RenderWidgetHostViewAura::OnTextSelectionChanged(
     ui::ScopedClipboardWriter clipboard_writer(ui::CLIPBOARD_TYPE_SELECTION);
     clipboard_writer.WriteText(selection->selected_text());
   }
-#endif  // defined(USE_X11) && !defined(OS_CHROMEOS)
+
+// #endif defined(USE_X11) && !defined(OS_CHROMEOS)
+#elif defined(OS_WIN)
+  // Some assistive software need to track the location of the caret.
+  if (!GetRenderWidgetHost())
+    return;
+
+  // Not using |GetCaretBounds| because it includes the whole of the selection,
+  // not just the focus.
+  const TextInputManager::SelectionRegion* region =
+      GetTextInputManager()->GetSelectionRegion(focused_view);
+  if (!region)
+    return;
+  gfx::Rect caret_rect = ConvertRectToScreen(gfx::Rect(
+      region->focus.edge_top_rounded().x(),
+      region->focus.edge_top_rounded().y(), 1, region->focus.GetHeight()));
+  ui::AXFakeCaretWin::Get()->MoveCaretTo(caret_rect);
+#endif  // defined(OS_WIN)
 }
 
 void RenderWidgetHostViewAura::SetPopupChild(