* Add tree tab collapse/expand UI and auto-expand on selection
- Add tree toggle button on BraveTab: when a tab has descendants, show
expand/collapse icon (replacing close button when applicable). When
the node is collapsed but has descendants, always show the toggle so
users can expand. Button uses submenu/expand icons per collapsed state.
- Model: BraveTabStripModel::SetTreeTabNodeCollapsed() updates collapse
state and notifies observers via TreeTabChange::kNodeCollapsedStateChanged.
TreeTabModel::GetClosestCollapsedAncestor() returns the closest collapsed
ancestor for a node.
- Controller: BraveBrowserTabStripController exposes
SetTreeTabNodeCollapsed(), IsInCollapsedTreeTabNode(), and
GetClosestCollapsedAncestor(). On collapsed-state change, updates the
tab’s tree toggle icon and invalidates layout.
- Tab strip: Override SetSelection() to post ExpandAllCollapsedAncestors();
when the user selects a tab (or adds an active new tab) that lives under
collapsed nodes, all ancestors are expanded so the selection is visible.
- Layout: TabStripLayoutHelper marks slots in collapsed tree nodes as
TabOpen::kClosed so those tabs are not laid out (hidden).
- Observer: Add TreeTabChange::CollapsedStateChangedChange and
kNodeCollapsedStateChanged. TabSlotController gains
SetTreeTabNodeCollapsed() and IsInCollapsedTreeTabNode(); TabSlotView
gains IsInCollapsedTreeTabNode(). Chromium overrides provide no-ops or
defaults.
- Tests: TreeTabsBrowserTest for auto-expand on selecting a tab in a
collapsed tree and on adding an active new tab; BraveTabTestWithTreeTab
for toggle visibility (replacing close button when has descendants, and
always visible when collapsed with descendants).
- TreeTabNode: add set_height_for_test() for unit tests.
Sangwoo Ko
86eda949d4