UI: use HIDE_HEADER for active tool in properties editor

Unfortunately this isn't yet compatible with category tabs,
define a duplicate panel only for the properties editor.

release/scripts/startup/bl_ui/space_view3d.py

@@ -4726,6 +4726,27 @@ class VIEW3D_PT_active_tool(Panel, ToolActivePanelHelper):
     bl_space_type = 'VIEW_3D'
     bl_region_type = 'UI'
     bl_category = "Tool"
+    # See comment below.
+    # bl_options = {'HIDE_HEADER'}
+
+    # Don't show in properties editor.
+    @classmethod
+    def poll(cls, context):
+        return context.area.type == 'VIEW_3D'
+
+
+# FIXME(campbell): remove this second panel once 'HIDE_HEADER' works with category tabs,
+# Currently pinning allows ordering headerless panels below panels with headers.
+class VIEW3D_PT_active_tool_duplicate(Panel, ToolActivePanelHelper):
+    bl_space_type = 'VIEW_3D'
+    bl_region_type = 'UI'
+    bl_category = "Tool"
+    bl_options = {'HIDE_HEADER'}
+
+    # Only show in properties editor.
+    @classmethod
+    def poll(cls, context):
+        return context.area.type != 'VIEW_3D'
 
 
 class VIEW3D_PT_view3d_properties(Panel):
@@ -6550,6 +6571,7 @@ classes = (
     VIEW3D_MT_orientations_pie,
     VIEW3D_MT_proportional_editing_falloff_pie,
     VIEW3D_PT_active_tool,
+    VIEW3D_PT_active_tool_duplicate,
     VIEW3D_PT_view3d_properties,
     VIEW3D_PT_view3d_lock,
     VIEW3D_PT_view3d_cursor,