Implement features in NativeViewHostAura for scroll end effect

ui/views/controls/native/native_view_host.h

Index: ui/views/controls/native/native_view_host.h
diff --git a/ui/views/controls/native/native_view_host.h b/ui/views/controls/native/native_view_host.h
index bdc51510550ca1569853639a0d615f1158159f28..15e286b135e352bd2ce1458a272caf5be35d7b8f 100644
--- a/ui/views/controls/native/native_view_host.h
+++ b/ui/views/controls/native/native_view_host.h
@@ -15,6 +15,38 @@ namespace views {
 class NativeViewHostAuraTest;
 class NativeViewHostWrapper;
 
+// When performing fast resizes the contents is not actually resized, but
+// instead the contents is positioned and clipped to give the impression of
+// resizing. Gravity indicates the positioning of the content relative to the
+// clipping. The default value, northwest, indicates that the top left corner of
+// the clip and the content should align, so the bottom and left sides of the

[sky, 2013/09/24 20:23:25]

left -> right

[rharrison, 2013/09/26 20:36:48]

Done.

+// content will be clipped. For a value like south the bottom edges will align
+// at their respective middles, thus the full vertical resize will be reflected
+// on the top, but half of the horizontal resize will be reflected on the left
+// and right sides. The following list is the gravity values and their alignment
+// points for reference, coordinates relative to the respective system for the
+// clip or contents:
+//   NorthWest      (0, 0)
+//   North          (width/2, 0)
+//   NorthEast      (width, 0)
+//   East           (width, height/2)
+//   SouthEast      (width, height)
+//   South          (width/2, height)
+//   SouthWest      (0, height)
+//   West           (0, height/2)
+//   Center         (width/2, height/2)
+enum FastResizeGravity {

[sky, 2013/09/24 20:23:25]

I'm not opposed to all of these, but do we really need them all?

[sky, 2013/09/24 20:23:25]

Could you also make this a member of NativeViewHost.

[rharrison, 2013/09/26 20:36:48]

The default is NW and I would need a southern one for the effect I am working
on, but we don't need them all at the moment. I was following along with what
Xlib does, so decided to do the 8 directions plus centre. 

I am peronally implementing them all since it seems a little weird to me to have
just a few of the directions implemented, but not all of them. The additional
directions don't require substantial or complex code to support them, just
additional simple case statements. If there needed to be special handling or
more involved code then I would be more concerned.

[rharrison, 2013/09/26 20:36:48]

Done.

+  FAST_RESIZE_GRAVITY_NORTHWEST,
+  FAST_RESIZE_GRAVITY_NORTH,
+  FAST_RESIZE_GRAVITY_NORTHEAST,
+  FAST_RESIZE_GRAVITY_EAST,
+  FAST_RESIZE_GRAVITY_SOUTHEAST,
+  FAST_RESIZE_GRAVITY_SOUTH,
+  FAST_RESIZE_GRAVITY_SOUTHWEST,
+  FAST_RESIZE_GRAVITY_WEST,
+  FAST_RESIZE_GRAVITY_CENTER,
+};
+
 // If a NativeViewHost's native view is a Widget, this native window
 // property is set on the widget, pointing to the owning NativeViewHost.
 extern const char kWidgetNativeViewHostKey[];
@@ -74,6 +106,18 @@ class VIEWS_EXPORT NativeViewHost : public View {
     return fast_resize_at_last_layout_;
   }
 
+  // Gravity controls how the clip is positioned relative to the native
+  // view. The specifics of this are discussed in the comment above the related
+  // enum. This call only sets the value being used, but does not cause a
+  // re-layout, so ShowWidget, via Layout, must be called before the new gravity
+  // will have an effect.
+  void set_fast_resize_gravity(FastResizeGravity gravity) {
+    fast_resize_gravity_ = gravity;
+  }
+  FastResizeGravity fast_resize_gravity() {
+    return fast_resize_gravity_;
+  }
+
   // Accessor for |native_view_|.
   gfx::NativeView native_view() const { return native_view_; }
 
@@ -123,6 +167,9 @@ class VIEWS_EXPORT NativeViewHost : public View {
   // Value of |fast_resize_| during the last call to Layout.
   bool fast_resize_at_last_layout_;
 
+  // gravity value to be used on the next call to ShowWidget.
+  FastResizeGravity fast_resize_gravity_;
+
   // The view that should be given focus when this NativeViewHost is focused.
   View* focus_view_;