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);

[Devlin, 2016/07/27 16:46:23]

For my own edification, what's the motivation behind this one?

[dcheng, 2016/07/27 17:02:36]

1. map::operator[] generates a bunch of inline code
2. the string literal to std::string conversion also generates a bunch of inline
code

Previously, we paid the cost of this every time we called feature_["literal"] =
std::move(feature);

Now, we only pay the cost once (in the definition of AddFeature). We still have
to pay a few instructions to set up this actual function call, but it still
works out to a pretty significant savings.

[Devlin, 2016/07/27 17:04:59]

Ah, makes sense.  Thanks!

 
  private:
+  std::map<std::string, std::unique_ptr<Feature>> features_;
+
   DISALLOW_COPY_AND_ASSIGN(BaseFeatureProvider);
 };