Reduce size of generated extension FeatureProviders.

extensions/common/features/base_feature_provider.h

Index: extensions/common/features/base_feature_provider.h
diff --git a/extensions/common/features/base_feature_provider.h b/extensions/common/features/base_feature_provider.h
index 59c16699d591324619808db6c8b919164b33ee95..5b6be3d3ce76d79a7673fd467e76f878a1a13d74 100644
--- a/extensions/common/features/base_feature_provider.h
+++ b/extensions/common/features/base_feature_provider.h
@@ -11,6 +11,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/strings/string_piece.h"
 #include "extensions/common/features/feature_provider.h"
 
 namespace extensions {
@@ -37,9 +38,12 @@ class BaseFeatureProvider : public FeatureProvider {
 
  protected:
   BaseFeatureProvider();
-  std::map<std::string, std::unique_ptr<Feature>> features_;
+
+  void AddFeature(base::StringPiece name, std::unique_ptr<Feature> feature);
 
  private:
+  std::map<std::string, std::unique_ptr<Feature>> features_;
+
   DISALLOW_COPY_AND_ASSIGN(BaseFeatureProvider);
 };