Introduce HostID and de-couple Extensions from "script injection System" [browser side]

chrome/browser/extensions/api/declarative_content/content_action.h

Index: chrome/browser/extensions/api/declarative_content/content_action.h
diff --git a/chrome/browser/extensions/api/declarative_content/content_action.h b/chrome/browser/extensions/api/declarative_content/content_action.h
index dc39431aed870bfe65d677064bf23bc30e542a05..48f4e72dac9e596bff73614452a2002949b35660 100644
--- a/chrome/browser/extensions/api/declarative_content/content_action.h
+++ b/chrome/browser/extensions/api/declarative_content/content_action.h
@@ -95,6 +95,15 @@ class RequestContentScript : public ContentAction {
  public:
   struct ScriptData;
 
+  // TODO(hanxi): add RulesRegistryID to the RequestKey.
+  struct RequestKey {
+    explicit RequestKey(const std::string& host_id) : host_id(host_id) {}
+    bool operator<(const RequestKey& key) const {
+      return host_id.compare(key.host_id) < 0;
+    }
+    std::string host_id;
+  };
+
   RequestContentScript(content::BrowserContext* browser_context,
                        const Extension* extension,
                        const ScriptData& script_data);
@@ -140,7 +149,7 @@ class RequestContentScript : public ContentAction {
   void InitScript(const Extension* extension, const ScriptData& script_data);
 
   void AddScript() {
-    DCHECK(master_);
+    DCHECK(master_.get());
     master_->AddScript(script_);
   }
 
@@ -150,7 +159,7 @@ class RequestContentScript : public ContentAction {
                                      const std::string& extension_id) const;
 
   UserScript script_;
-  DeclarativeUserScriptMaster* master_;
+  linked_ptr<DeclarativeUserScriptMaster> master_;
 
   DISALLOW_COPY_AND_ASSIGN(RequestContentScript);
 };