Tab Strip: Fix bad revert

This fixes a bad revert of the tab strip in the below CL
https://crrev.com/c/2487252

Bug: 1099917
Change-Id: Ied10f472e699daadb280640f7455fc3685cb9826
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2490490Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819667}

chrome/browser/ui/views/tabs/tab_strip.cc

@@ -781,7 +781,7 @@ class TabStrip::TabDragContextImpl : public TabDragContext {
     // Immediately hide the new tab button if the last tab is being dragged.
     const Tab* last_visible_tab = tab_strip_->GetLastVisibleTab();
     if (last_visible_tab && last_visible_tab->dragging())
-      SetNewTabButtonVisible(true);
+      SetNewTabButtonVisible(false);
 
     std::vector<gfx::Rect> bounds = CalculateBoundsForDraggedViews(views);
     DCHECK_EQ(views.size(), bounds.size());