shelf: Allow directly dragging items from main shelf to overflow.

ash/shelf/shelf_view.cc

Index: ash/shelf/shelf_view.cc
diff --git a/ash/shelf/shelf_view.cc b/ash/shelf/shelf_view.cc
index 7304bd833f8478e2823df4c978aca5b965e8ca8a..dae918888a9b1c9f8f1a28f0c947e3868523e116 100644
--- a/ash/shelf/shelf_view.cc
+++ b/ash/shelf/shelf_view.cc
@@ -1133,10 +1133,26 @@ bool ShelfView::HandleRipOffDrag(const ui::LocatedEvent& event) {
     UpdateDragIconProxy(screen_location);
     return true;
   }
-  // Check if we are too far away from the shelf to enter the ripped off state.
-  // Determine the distance to the shelf.
+
+  // Determine if we should enter the ripped off state. We should enter if:

[msw, 2017/06/06 00:27:23]

nit: "Mark the item as dragged off the shelf if the drag distance exceeds
kRipOffDistance, or if it's dragged between the main and overflow shelf."

[sammiequon, 2017/06/06 16:21:26]

Done.

+  // 1) The item is dragged more than |kRipOffDistance| from the shelf.
+  // 2) We are on the overflow shelf and the item is dragged onto the main
+  // shelf.
+  // 3) We are on the main shelf and the item is dragged onto the overflow
+  // shelf.
   int delta = CalculateShelfDistance(screen_location);
-  if (delta > kRipOffDistance) {
+  bool enableRipOff = delta > kRipOffDistance;

[msw, 2017/06/06 00:27:23]

Use the unix_hacker naming convention in Chrome's C++ code |drag_off_shelf|, or
just use the |dragged_off_shelf_| member, or just inline the conditionals into
the if statement.

[sammiequon, 2017/06/06 16:21:26]

Done.

+  enableRipOff =
+      enableRipOff ||

[msw, 2017/06/06 00:27:23]

nit: if you keep separate statements like this, then use |= instead of = ... ||

[sammiequon, 2017/06/06 16:21:26]

Done.

+      (is_overflow_mode() &&
+       main_shelf_->GetBoundsForDragInsertInScreen().Contains(screen_location));
+  enableRipOff = enableRipOff || (!is_overflow_mode() && overflow_bubble_ &&
+                                  overflow_bubble_->IsShowing() &&
+                                  overflow_bubble_->shelf_view()
+                                      ->GetBoundsForDragInsertInScreen()
+                                      .Contains(screen_location));
+
+  if (enableRipOff) {
     // Create a proxy view item which can be moved anywhere.
     CreateDragIconProxy(event.root_location(), drag_view_->GetImage(),
                         drag_view_, gfx::Vector2d(0, 0),