Add ability to drag tabs between pinned and unpinned tabs to modify the

pinned state.

Bug: 965681
Change-Id: I4cebf850839a1fdbee702ab2cd3c2fccbdba811e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1637045Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#666796}

chrome/browser/ui/views/tabs/tab_drag_controller.h

@@ -14,6 +14,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/timer/timer.h"
 #include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+#include "chrome/browser/ui/views/tabs/tab_animation_state.h"
 #include "chrome/browser/ui/views/tabs/tab_drag_context.h"
 #include "chrome/browser/ui/views/tabs/tab_strip_types.h"
 #include "ui/base/models/list_selection_model.h"
@@ -494,6 +495,19 @@ class TabDragController : public views::WidgetObserver {
   // is showing a modal).
   bool ShouldDisallowDrag(gfx::NativeWindow window);
 
+  // Helper method for TabDragController::MoveAttached to update the pinnedness
+  // of the tab being moved by checking the pinnedness of the tabs being
+  // dragged with the pinnedness of the tab at the target dragged location.
+  // TODO (crbug.com/971676): This will swap and update the pinnedness of
+  // multi-selected tabs one at a time, which is unintended.
+  void UpdatePinnednessOfDraggedTab(int to_index);
+
+  // Helper method that checks if the index is valid in the TabDragContext and
+  // the pin at the index has the expected pinned value.
+  bool CheckValidPinnedness(
+      int index,
+      TabAnimationState::TabPinnedness expected_pinnedness);
+
   EventSource event_source_;
 
   // The TabDragContext the drag originated from. This is set to null