Draw web content area correctly on a phantom window for window dragging

ash/wm/window_util.cc

Index: ash/wm/window_util.cc
diff --git a/ash/wm/window_util.cc b/ash/wm/window_util.cc
index 0b71f068d51ab604660ca1153b99605585f1563f..070015156c7116ddf09b021e3b827ed8d1c10330 100644
--- a/ash/wm/window_util.cc
+++ b/ash/wm/window_util.cc
@@ -4,6 +4,8 @@
 
 #include "ash/wm/window_util.h"
 
+#include <vector>
+
 #include "ash/shell.h"
 #include "ash/wm/activation_controller.h"
 #include "ash/wm/window_properties.h"
@@ -12,6 +14,7 @@
 #include "ui/aura/root_window.h"
 #include "ui/aura/window.h"
 #include "ui/base/ui_base_types.h"
+#include "ui/compositor/layer.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/screen.h"
 
@@ -99,5 +102,35 @@ void CenterWindow(aura::Window* window) {
   window->SetBounds(center);
 }
 
+ui::Layer* RecreateWindowLayers(aura::Window* window) {
+  const gfx::Rect bounds = window->bounds();
+  ui::Layer* old_layer = window->RecreateLayer();
+  DCHECK(old_layer);
+  // Resize the window to the new size, which will force a layout and paint.
+  window->SetBounds(bounds);
+  for (aura::Window::Windows::const_iterator it = window->children().begin();
+       it != window->children().end();
+       ++it) {
+    aura::Window* child = *it;
+    const gfx::Rect child_bounds = child->bounds();
+    ui::Layer* old_child_layer = RecreateWindowLayers(child);
+    // Maintain the hierarchy of the detached layers.
+    old_layer->Add(old_child_layer);
+    child->SetBounds(child_bounds);  // Resize the child window too.
+  }
+  return old_layer;
+}
+
+void DeepDeleteLayers(ui::Layer* layer) {
+  std::vector<ui::Layer*> children = layer->children();
+  for (std::vector<ui::Layer*>::const_iterator it = children.begin();
+       it != children.end();
+       ++it) {
+    ui::Layer* child = *it;
+    DeepDeleteLayers(child);
+  }
+  delete layer;
+}
+
 }  // namespace wm
 }  // namespace ash