Move user menu back into the work area if it extends too far down.

Also shifts the user menu right in this case so that the dropdown arrow
remains visible.

Bug: 861791
Change-Id: I65b0be969c1f15936ce3b86df5bae4eb7c200ed6
Reviewed-on: https://chromium-review.googlesource.com/1129847Reviewed-by: Jacob Dufault <jdufault@chromium.org>
Commit-Queue: Quan Nguyen <qnnguyen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573482}

ash/login/ui/login_bubble.cc

@@ -320,6 +320,7 @@ class LoginUserMenuView : public LoginBaseBubbleView,
       SetSize(GetPreferredSize());
       SizeToContents();
       Layout();
+      EnsureWidgetInWorkArea();
       if (on_remove_user_warning_shown_)
         std::move(on_remove_user_warning_shown_).Run();
       return;
@@ -333,6 +334,26 @@ class LoginUserMenuView : public LoginBaseBubbleView,
       std::move(on_remove_user_requested_).Run();
   }
 
+  void EnsureWidgetInWorkArea() {
+    const int view_bottom = GetBoundsInScreen().bottom();
+    const int work_area_bottom =
+        display::Screen::GetScreen()
+            ->GetDisplayNearestWindow(GetWidget()->GetNativeWindow())
+            .work_area()
+            .bottom();
+
+    if (work_area_bottom >= view_bottom)
+      return;
+
+    // If the bubble extends into the shelf, move the bubble up so that the
+    // bottom edge just touches the top of the shelf. Also shift the bubble
+    // right so that the anchor (arrow) remains visible.
+    set_anchor_view_insets(anchor_view_insets().Offset(gfx::Vector2d(
+        GetAnchorView()->GetBoundsInScreen().right() - GetBoundsInScreen().x(),
+        work_area_bottom - view_bottom)));
+    OnAnchorBoundsChanged();
+  }
+
   views::View* remove_user_button() { return remove_user_button_; }
 
   views::View* remove_user_confirm_data() { return remove_user_confirm_data_; }