Simplify painting of Tab Group dragging highlight

Remove the ShouldPaint logic in TabGroupView because it's already handled in TabStrip::PaintChildren(): https://cs.chromium.org/chromium/src/chrome/browser/ui/views/tabs/tab_strip.cc?l=2088&rcl=2170efeafe8ee9cafa678d8d1bae67f8182798a8

Also simplify TabStrip::StoppedDraggingView(), which was handling group headers in a hacky way. The group header handling is now more explicit and separate from the deleted-tab logic.

Bug: 1034169
Change-Id: I7e87387e6cb89863cb6a0d4b5b706c3ef14d780e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1988678
Commit-Queue: Connie Wan <connily@chromium.org>
Reviewed-by: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#728689}

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

@@ -23,9 +23,6 @@ TabGroupHighlight::TabGroupHighlight(TabGroupViews* tab_group_views,
 }
 
 void TabGroupHighlight::OnPaint(gfx::Canvas* canvas) {
-  if (!tab_group_views_->ShouldPaintGroupBackground())
-    return;
-
   SetBoundsRect(tab_group_views_->GetBounds());
 
   SkPath path = GetPath();

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

@@ -91,7 +91,3 @@ SkColor TabGroupViews::GetGroupBackgroundColor() const {
                                        TabStyle::kSelectedTabOpacity,
                                        SK_AlphaTRANSPARENT, SK_AlphaOPAQUE));
 }
-
-bool TabGroupViews::ShouldPaintGroupBackground() const {
-  return header_->dragging();
-}

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

@@ -49,10 +49,6 @@ class TabGroupViews {
   // tab color. Needed to layer painting for the group background highlight.
   SkColor GetGroupBackgroundColor() const;
 
-  // Returns whether the group highlight background should be shown. Currently
-  // it should only be shown if the entire group is dragging via its header.
-  bool ShouldPaintGroupBackground() const;
-
  private:
   TabStrip* const tab_strip_;
   const tab_groups::TabGroupId group_;

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

@@ -2686,14 +2686,16 @@ void TabStrip::OnGroupCloseAnimationCompleted(
 }
 
 void TabStrip::StoppedDraggingView(TabSlotView* view, bool* is_first_view) {
+  if (view &&
+      view->GetTabSlotViewType() == TabSlotView::ViewType::kTabGroupHeader) {
+    // Ensure all tab group UI is repainted, especially the dragging highlight.
+    view->set_dragging(false);
+    SchedulePaint();
+    return;
+  }
+
   int tab_data_index = GetModelIndexOf(view);
   if (tab_data_index == -1) {
-    // Ensure the drag status is updated even if the view is not a valid tab.
-    // This is primarily to make sure group headers are updated correctly.
-    // Otherwise, tab drag status is only updated in PrepareForAnimation().
-    if (view)
-      view->set_dragging(false);
-
     // The tab was removed before the drag completed. Don't do anything.
     return;
   }

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

@@ -1230,13 +1230,6 @@ TEST_P(TabStripTest, GroupHighlightBasics) {
   std::vector<TabGroupViews*> views = ListGroupViews();
   EXPECT_EQ(1u, views.size());
 
-  // Highlights should not be painted by default.
-  EXPECT_FALSE(views[0]->ShouldPaintGroupBackground());
-
-  // Highlights should be painted when the group header is dragging.
-  views[0]->header()->set_dragging(true);
-  EXPECT_TRUE(views[0]->ShouldPaintGroupBackground());
-
   // The highlight bounds match the group view bounds. Grab this manually
   // here, since there isn't a real paint cycle to trigger OnPaint().
   gfx::Rect bounds = views[0]->GetBounds();