[Payments] Implements the credit card editor for Desktop UI

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

Index: chrome/browser/ui/views/payments/view_stack.h
diff --git a/chrome/browser/ui/views/payments/view_stack.h b/chrome/browser/ui/views/payments/view_stack.h
index f29feac0cc005219d1eb95a62843e360a13b440e..3699ef291fb53bdf776b9bb4e2738b05a0df9aff 100644
--- a/chrome/browser/ui/views/payments/view_stack.h
+++ b/chrome/browser/ui/views/payments/view_stack.h
@@ -9,6 +9,10 @@
 #include "ui/views/animation/bounds_animator.h"
 #include "ui/views/animation/bounds_animator_observer.h"
 
+namespace payments {
+class PaymentRequestInteractiveTestBase;
+}  // namespace payments
+

[please use gerrit instead, 2017/02/02 20:19:03]

Is this forward declaration necessary?

[Mathieu, 2017/02/03 02:18:57]

Yes :\ It was cryptic to me why it was needed; someone explained that without
it, the "friend class" statement below does not know what the symbol is, and
compiler may think we are just declaring an inner class. 

 // This view represents a stack of views that slide in over one another from
 // left to right. It manages the animation and lifetime of views that are
 // pushed and popped on it. To use this class, add it to a view hierarchy, and
@@ -43,6 +47,7 @@ class ViewStack : public views::BoundsAnimatorObserver,
   FRIEND_TEST_ALL_PREFIXES(ViewStackTest, TestPushStateAddsViewToChildren);
   FRIEND_TEST_ALL_PREFIXES(ViewStackTest, TestLayoutUpdatesAnimations);
   friend class ViewStackTest;
+  friend class payments::PaymentRequestInteractiveTestBase;
 
   // Returns the top state of the stack, used in tests.
   views::View* top() { return stack_.back().get(); }