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..f9d6ae6aa711a8761717d2f94f0c936e49bfe545 100644
--- a/ui/base/material_design/material_design_controller.h
+++ b/ui/base/material_design/material_design_controller.h
@@ -28,6 +28,14 @@ class UI_BASE_EXPORT MaterialDesignController {
     MATERIAL_HYBRID = 2
   };
 
+  // The extent to which the mode applies.
+  enum Extent {
+    // Only apply the Material Design modes to primary UI (toolbar, etc.).
+    PRIMARY = 0,
+    // Apply the Material Design modes to secondary UI (bubble contents, etc.).
+    SECONDARY = 1,
+  };
+
   // Initializes |mode_|. Must be called before checking |mode_|.
   static void Initialize();
 
@@ -37,6 +45,10 @@ 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 +62,9 @@ class UI_BASE_EXPORT MaterialDesignController {
   // The current Mode to be used by the system.
   static Mode mode_;
 
+  // The extent to apply |mode_|.
+  static Extent extent_;

[varkha, 2016/04/27 23:06:05]

You would probably want to save / restore the mode here:
https://code.google.com/p/chromium/codesearch#chromium/src/ui/base/test/mater...

This is used to ensure that the tests do not change global state when a shard
runs multiple tests.

[Evan Stade, 2016/04/27 23:20:40]

I think this would make sense as soon as we decide we need a test that changes
|extent_|.

[varkha, 2016/04/27 23:30:58]

True but easy to forget and the results may be flaky rather than just failures.
I think it is easier to keep this atomic.

+
   // Declarations only. Do not allow construction of an object.
   MaterialDesignController();
   ~MaterialDesignController();