Revert "Reland "Add ability to drag tabs between pinned and unpinned tabs to modify the""

This reverts commit 2af55fab.

Reason for revert: Still flaky

Original change's description:
> Reland "Add ability to drag tabs between pinned and unpinned tabs to modify the"
> 
> This reverts commit 1158f5ef.
> 
> Reason for revert: This is an experimental reland since this broke older
> mac waterfall bots. This was fixed with https://chromium-review.googlesource.com/c/chromium/src/+/1649313
> 
> Original change's description:
> > Revert "Add ability to drag tabs between pinned and unpinned tabs to modify the"
> >
> > This reverts commit 91948560.
> >
> > Reason for revert: https://ci.chromium.org/p/chromium/builders/ci/Mac10.11%20Tests/38757, consistent failures on mac of the following tests:
> > TabDragging/DetachToBrowserTabDragControllerTest.DragToPinEnabled_DragToUnpinInNewWindow/0
> > TabDragging/DetachToBrowserTabDragControllerTest.DragToPinInNewWindow/0
> >
> > Original change's description:
> > > 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/+/1637045
> > > Reviewed-by: Bret Sepulveda <bsep@chromium.org>
> > > Commit-Queue: Charlene Yan <cyan@chromium.org>
> > > Cr-Commit-Position: refs/heads/master@{#666796}
> >
> > TBR=bsep@chromium.org,cyan@chromium.org
> >
> > Change-Id: I0a68811b31c718fcdccba6058ab6bdf664a1547a
> > No-Presubmit: true
> > No-Tree-Checks: true
> > No-Try: true
> > Bug: 965681
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1649316
> > Reviewed-by: Armando Miraglia <armax@chromium.org>
> > Commit-Queue: Armando Miraglia <armax@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#667042}
> 
> TBR=bsep@chromium.org,armax@chromium.org,cyan@chromium.org
> 
> Change-Id: Ia1521f2c2443c40a3b2ac55be079c6e1be91dea2
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 965681
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1648899
> Commit-Queue: Charlene Yan <cyan@chromium.org>
> Reviewed-by: Charlene Yan <cyan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#669906}

TBR=bsep@chromium.org,armax@chromium.org,cyan@chromium.org

Change-Id: I8ab3f943b2aed204f318c329fca88a0459f2255b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 965681
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1663582Reviewed-by: Charlene Yan <cyan@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#669934}

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

@@ -14,7 +14,6 @@
 #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"
@@ -495,19 +494,6 @@ 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