Introduce new flag to control usage of MD in secondary (not top-chrome)

ui/base/material_design/material_design_controller.h

Index: ui/base/material_design/material_design_controller.h
diff --git a/ui/base/material_design/material_design_controller.h b/ui/base/material_design/material_design_controller.h
index fb58f0bf25a4b9dd984442e8f7ae77a87aa11cea..46363f776b1a3622726865439f3f60def1e5db5c 100644
--- a/ui/base/material_design/material_design_controller.h
+++ b/ui/base/material_design/material_design_controller.h
@@ -37,6 +37,10 @@ class UI_BASE_EXPORT MaterialDesignController {
   // Returns true if the current mode is a material design variant.
   static bool IsModeMaterial();
 
+  // Returns true if the current mode is a material design variant and this mode
+  // should be extended to cover secondary UI.
+  static bool IsSecondaryUiMaterial();
+
   // Returns the per-platform default material design variant.
   static Mode DefaultMode();
 
@@ -50,6 +54,10 @@ class UI_BASE_EXPORT MaterialDesignController {
   // The current Mode to be used by the system.
   static Mode mode_;
 
+  // True when |mode_| applies beyond the primary UI (toolbar, tabstrip,
+  // etc.). For example, this controls use of MD inside bubbles and dialogs.
+  static bool include_secondary_ui_;
+
   // Declarations only. Do not allow construction of an object.
   MaterialDesignController();
   ~MaterialDesignController();