[Web Payments] Add PopMany and Size functions to ViewStack

chrome/browser/ui/views/payments/view_stack.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/views/payments/view_stack.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
@@ skipping 41 matching lines @@
 }
 
 void ViewStack::Pop() {
   gfx::Rect destination = bounds();
   destination.set_origin(gfx::Point(width(), 0));
 
   slide_out_animator_->AnimateViewTo(
       stack_.back().get(), destination);
 }
 
+void ViewStack::PopMany(int n) {
+  DCHECK_LT(static_cast<size_t>(n), size());  // The stack can never be empty.
+
+  size_t pre_size = stack_.size();
+  // Erase N - 1 elements now, the last one will be erased when its animation
+  // completes
+  stack_.erase(stack_.end() - n, stack_.end() - 1);
+  DCHECK_EQ(pre_size - n + 1, stack_.size());
+
+  Pop();
+}
+
+size_t ViewStack::size() const {
+  return stack_.size();
+}
+
 bool ViewStack::CanProcessEventsWithinSubtree() const {
   return !slide_in_animator_->IsAnimating() &&
          !slide_out_animator_->IsAnimating();
 }
 
 void ViewStack::Layout() {
   views::View::Layout();
 
   // If this view's bounds changed since the beginning of an animation, the
   // animator's targets have to be changed as well.
@@ skipping 21 matching lines @@
 }
 
 void ViewStack::OnBoundsAnimatorDone(views::BoundsAnimator* animator) {
   // This should only be called from slide_out_animator_ when the views going
   // out are done animating.
   DCHECK_EQ(animator, slide_out_animator_.get());
 
   stack_.pop_back();
   DCHECK(!stack_.empty()) << "State stack should never be empty";
 }