cros: Hide stylus tools on various sign-in screens, disable active mode when inserting stylus.

ash/common/system/chromeos/palette/palette_tool_manager.h

Index: ash/common/system/chromeos/palette/palette_tool_manager.h
diff --git a/ash/common/system/chromeos/palette/palette_tool_manager.h b/ash/common/system/chromeos/palette/palette_tool_manager.h
index 198757c8c8a70560aa0f2efd9ef6142078c5d5b3..dbf98801cb668e16048ceb69e795f48fc0c188ff 100644
--- a/ash/common/system/chromeos/palette/palette_tool_manager.h
+++ b/ash/common/system/chromeos/palette/palette_tool_manager.h
@@ -90,6 +90,9 @@ class ASH_EXPORT PaletteToolManager : public PaletteTool::Delegate {
   // should clear any (now) stale references.
   void NotifyViewsDestroyed();
 
+  // Helper method to disable any active tool in the given |group|.
+  void DisableActiveTool(PaletteGroup group);
+
  private:
   // PaleteTool::Delegate overrides.
   void EnableTool(PaletteToolId tool_id) override;