ash: Refactor some code that snaps windows.

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 3adb2968049eadccb5da5e65493634e3691b9d19..460b9c35f16acf15bb8015915f2e8fa6f4e3813e 100644
--- a/ash/wm/window_util.cc
+++ b/ash/wm/window_util.cc
@@ -86,7 +86,8 @@ bool CanResizeWindow(const aura::Window* window) {
 
 bool CanSnapWindow(aura::Window* window) {
   // If a window has a maximum size defined, snapping may make it too big.
-  return window->delegate()->GetMaximumSize().IsEmpty();
+  return window->delegate() ? window->delegate()->GetMaximumSize().IsEmpty() :
+                              true;
 }
 
 bool IsWindowNormal(const aura::Window* window) {
@@ -139,6 +140,27 @@ void CenterWindow(aura::Window* window) {
   window->SetBounds(center);
 }
 
+void SnapWindow(aura::Window* window, internal::SnapSizer::Edge edge) {
+  if (!CanSnapWindow(window))
+    return;
+  internal::SnapSizer sizer(window, gfx::Point(), edge,
+      internal::SnapSizer::OTHER_INPUT);
+  if (wm::IsWindowFullscreen(window) || wm::IsWindowMaximized(window)) {
+    // Before we can set the bounds we need to restore the window.
+    // Restoring the window will set the window to its restored bounds.
+    // To avoid an unnecessary bounds changes (which may have side effects)
+    // we set the restore bounds to the bounds we want, restore the window,
+    // then reset the restore bounds. This way no unnecessary bounds
+    // changes occurs and the original restore bounds is remembered.
+    gfx::Rect restore = *GetRestoreBoundsInScreen(window);
+    SetRestoreBoundsInParent(window, sizer.GetSnapBounds(window->bounds()));
+    wm::RestoreWindow(window);
+    SetRestoreBoundsInScreen(window, restore);
+  } else {
+    window->SetBounds(sizer.GetSnapBounds(window->bounds()));
+  }
+}
+
 ui::Layer* RecreateWindowLayers(aura::Window* window, bool set_bounds) {
   const gfx::Rect bounds = window->bounds();
   ui::Layer* old_layer = window->RecreateLayer();