Optimize ExtensionAPI::IsAnyFeatureAvailableToContext from O(#features) to O(#children + log #features).

This also replaces O(N) string allocations with 1 and moves the top-level
feature check to the top of the function to provide a quick exit when the
context has full access.

And it adds an IsAvailable() overload taking a Feature to avoid the string
copies in GetFeatureDependency().

BUG=305000

Review URL: https://codereview.chromium.org/107473004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241706 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 18 insertions, 14 deletions

diff --git a/extensions/common/extension_api.cc b/extensions/common/extension_api.cc
index 13c1ce3..710dc51 100644
--- a/extensions/common/extension_api.cc
+++ b/extensions/common/extension_api.cc
@@ -282,21 +282,19 @@ bool ExtensionAPI::IsAnyFeatureAvailableToContext(const Feature& api,
                                                   const GURL& url) {
   FeatureProviderMap::iterator provider = dependency_providers_.find("api");
   CHECK(provider != dependency_providers_.end());
-  const std::vector<std::string>& features =
-      provider->second->GetAllFeatureNames();
+  if (IsAvailable(api, extension, context, url).is_available())
+    return true;
 
   // Check to see if there are any parts of this API that are allowed in this
   // context.
-  for (std::vector<std::string>::const_iterator i = features.begin();
-       i != features.end(); ++i) {
-    const std::string& feature_name = *i;
-    if (feature_name != api.name() &&
-        feature_name.find(api.name() + ".") == 0) {
-      if (IsAvailable(feature_name, extension, context, url).is_available())
-        return true;
-    }
+  const std::vector<Feature*> features = provider->second->GetChildren(api);
+  for (std::vector<Feature*>::const_iterator feature = features.begin();
+       feature != features.end();
+       ++feature) {
+    if (IsAvailable(**feature, extension, context, url).is_available())
+      return true;
   }
-  return IsAvailable(api.name(), extension, context, url).is_available();
+  return false;
 }
 
 Feature::Availability ExtensionAPI::IsAvailable(const std::string& full_name,
@@ -305,14 +303,20 @@ Feature::Availability ExtensionAPI::IsAvailable(const std::string& full_name,
                                                 const GURL& url) {
   Feature* feature = GetFeatureDependency(full_name);
   CHECK(feature) << full_name;
+  return IsAvailable(*feature, extension, context, url);
+}
 
+Feature::Availability ExtensionAPI::IsAvailable(const Feature& feature,
+                                                const Extension* extension,
+                                                Feature::Context context,
+                                                const GURL& url) {
   Feature::Availability availability =
-      feature->IsAvailableToContext(extension, context, url);
+      feature.IsAvailableToContext(extension, context, url);
   if (!availability.is_available())
     return availability;
 
-  for (std::set<std::string>::iterator iter = feature->dependencies().begin();
-       iter != feature->dependencies().end(); ++iter) {
+  for (std::set<std::string>::iterator iter = feature.dependencies().begin();
+       iter != feature.dependencies().end(); ++iter) {
     Feature::Availability dependency_availability =
         IsAvailable(*iter, extension, context, url);
     if (!dependency_availability.is_available())