Revert of FrameGenerator should not be created until an AcceleratedWidget is available

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 6d32827f0b7947b72cf10d2ca98cb7f491b6a6b1..6f8c8d67bb6008827c277116ca3548c6f302e53f 100644
--- a/services/ui/ws/platform_display_default.cc
+++ b/services/ui/ws/platform_display_default.cc
@@ -35,10 +35,11 @@
 #if !defined(OS_ANDROID)
       image_cursors_(new ImageCursors),
 #endif
+      frame_generator_(new FrameGenerator(this, init_params.root_window)),
       metrics_(init_params.metrics),
-      widget_(gfx::kNullAcceleratedWidget),
-      root_window_(init_params.root_window),
-      init_device_scale_factor_(init_params.metrics.device_scale_factor) {
+      widget_(gfx::kNullAcceleratedWidget) {
+  frame_generator_->SetDeviceScaleFactor(
+      init_params.metrics.device_scale_factor);
 }
 
 PlatformDisplayDefault::~PlatformDisplayDefault() {
@@ -147,8 +148,7 @@
   }
 
   metrics_ = metrics;
-  if (frame_generator_)
-    frame_generator_->SetDeviceScaleFactor(metrics_.device_scale_factor);
+  frame_generator_->SetDeviceScaleFactor(metrics_.device_scale_factor);
   return true;
 }
 
@@ -178,8 +178,7 @@
 }
 
 void PlatformDisplayDefault::OnDamageRect(const gfx::Rect& damaged_region) {
-  if (frame_generator_)
-    frame_generator_->OnWindowDamaged();
+  frame_generator_->OnWindowDamaged();
 }
 
 void PlatformDisplayDefault::DispatchEvent(ui::Event* event) {
@@ -248,9 +247,7 @@
   DCHECK_EQ(gfx::kNullAcceleratedWidget, widget_);
   widget_ = widget;
   delegate_->OnAcceleratedWidgetAvailable();
-  frame_generator_ =
-      base::MakeUnique<FrameGenerator>(this, root_window_, widget_);
-  frame_generator_->SetDeviceScaleFactor(init_device_scale_factor_);
+  frame_generator_->OnAcceleratedWidgetAvailable(widget);
 }
 
 void PlatformDisplayDefault::OnAcceleratedWidgetDestroyed() {