Add support to the UI Service to run it inside the browser's process.

services/ui/ws/platform_display_default.cc

Index: services/ui/ws/platform_display_default.cc
diff --git a/services/ui/ws/platform_display_default.cc b/services/ui/ws/platform_display_default.cc
index 0b4bf025b6efdbcee7683c0389be84a67daafb22..9676c90134ec4ec4ad5c62738da6bfa38aa123b7 100644
--- a/services/ui/ws/platform_display_default.cc
+++ b/services/ui/ws/platform_display_default.cc
@@ -11,7 +11,7 @@
 #include "services/ui/display/screen_manager.h"
 #include "services/ui/public/interfaces/cursor/cursor_struct_traits.h"
 #include "services/ui/ws/server_window.h"
-#include "ui/base/cursor/image_cursors.h"
+#include "services/ui/ws/threaded_image_cursors.h"
 #include "ui/display/display.h"
 #include "ui/events/event.h"
 #include "ui/events/event_utils.h"
@@ -35,7 +35,7 @@ namespace ws {
 PlatformDisplayDefault::PlatformDisplayDefault(
     ServerWindow* root_window,
     const display::ViewportMetrics& metrics,
-    std::unique_ptr<ImageCursors> image_cursors)
+    std::unique_ptr<ThreadedImageCursors> image_cursors)
     : root_window_(root_window),
       image_cursors_(std::move(image_cursors)),
       metrics_(metrics),
@@ -46,9 +46,11 @@ PlatformDisplayDefault::~PlatformDisplayDefault() {
   delegate_ = nullptr;
 
   frame_generator_.reset();
+  image_cursors_.reset();
   // Destroy the PlatformWindow early on as it may call us back during
   // destruction and we want to be in a known state. But destroy the surface
-  // first because it can still be using the platform window.
+  // and ThreadedImageCursors first because they can still be using the platform
+  // window.
   platform_window_.reset();
 }
 
@@ -104,12 +106,15 @@ void PlatformDisplayDefault::SetCursor(const ui::CursorData& cursor_data) {
   if (!image_cursors_)
     return;
 
-  ui::Cursor native_cursor(cursor_data.cursor_type());
+  ui::CursorType cursor_type = cursor_data.cursor_type();
 
 #if defined(USE_OZONE)
-  if (cursor_data.cursor_type() != ui::CursorType::kCustom) {
-    image_cursors_->SetPlatformCursor(&native_cursor);
+  if (cursor_type != ui::CursorType::kCustom) {
+    // |platform_window_| is destroyed after |image_cursors_|, so it is
+    // guaranteed to outlive |image_cursors_|.
+    image_cursors_->SetCursor(cursor_type, platform_window_.get());
   } else {
+    ui::Cursor native_cursor(cursor_type);
     // In Ozone builds, we have an interface available which turns bitmap data
     // into platform cursors.
     ui::CursorFactoryOzone* cursor_factory =
@@ -118,6 +123,7 @@ void PlatformDisplayDefault::SetCursor(const ui::CursorData& cursor_data) {
         cursor_data.cursor_frames(), cursor_data.hotspot_in_pixels(),
         cursor_data.frame_delay().InMilliseconds(),
         cursor_data.scale_factor()));
+    platform_window_->SetCursor(native_cursor.platform());
   }
 #else
   // Outside of ozone builds, there isn't a single interface for creating
@@ -129,14 +135,12 @@ void PlatformDisplayDefault::SetCursor(const ui::CursorData& cursor_data) {
   // cursor management on its own mus windows so we can remove Webcursor from
   // //content/ and do this in way that's safe cross-platform, instead of as an
   // ozone-specific hack.
-  if (cursor_data.cursor_type() == ui::CursorType::kCustom) {
+  if (cursor_type == ui::CursorType::kCustom) {
     NOTIMPLEMENTED() << "No custom cursor support on non-ozone yet.";
-    native_cursor = ui::Cursor(ui::CursorType::kPointer);
+    cursor_type = ui::CursorType::kPointer;
   }
-  image_cursors_->SetPlatformCursor(&native_cursor);
+  image_cursors_->SetCursor(cursor_type, platform_window_.get());
 #endif
-
-  platform_window_->SetCursor(native_cursor.platform());
 }
 
 void PlatformDisplayDefault::MoveCursorTo(