Refactor intra-strip panel drags by introducing PanelDragController.

chrome/browser/ui/panels/overflow_panel_strip.cc

Index: chrome/browser/ui/panels/overflow_panel_strip.cc
diff --git a/chrome/browser/ui/panels/overflow_panel_strip.cc b/chrome/browser/ui/panels/overflow_panel_strip.cc
index 446dcb0bd6b377e43e8c18f45ec2e670bf3f2bb3..a3f2e4a1c17bc0a78f70ae84caa57f087621eff7 100644
--- a/chrome/browser/ui/panels/overflow_panel_strip.cc
+++ b/chrome/browser/ui/panels/overflow_panel_strip.cc
@@ -98,7 +98,6 @@ void OverflowPanelStrip::AddPanel(Panel* panel) {
 
   // Set panel properties for this strip.
   panel->SetAppIconVisibility(false);
-  panel->set_draggable(false);
   panel->ApplyVisualStyleForStrip();
 
   if (num_panels() == 1) {
@@ -182,6 +181,23 @@ void OverflowPanelStrip::RestorePanel(Panel* panel) {
   docked_strip->RestorePanel(panel);
 }
 
+bool OverflowPanelStrip::CanDragPanel(Panel* panel) const {
+  // All overflow panels are not draggable.
+  return false;
+}
+
+void OverflowPanelStrip::StartDraggingPanel(Panel* panel) {
+  NOTREACHED();
+}
+
+void OverflowPanelStrip::DragPanel(int delta_x, int delta_y) {
+  NOTREACHED();
+}
+
+void OverflowPanelStrip::EndDraggingPanel(bool cancelled) {
+  NOTREACHED();
+}
+
 void OverflowPanelStrip::RefreshLayout() {
   if (panels_.empty())
     return;