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_;

[Devlin, 2015/01/14 16:45:08]

I don't think it's wise to make this a linked_ptr.  Instead, let's document why
the weak pointer is safe.

[Xi Han, 2015/01/14 23:46:02]

linked_ptr was removed from here. Also I have to do a sacrifice here: use a raw
pointer. I tried the WeakPtr, but it is difficult to initialize master_ in the
constructor's initialization list, and I believe it is the only way to
initialize a WeakPtr:( Please correct me if I am wrong, I would like to make it
a weak pointer as well.

[Devlin, 2015/01/16 17:05:03]

That's my bad - when I say "weak pointer", I mean c-style raw pointer (i.e., one
that is weak and "dumb").  I need to fix that.  Raw pointer is fine, as long as
we document why it is safe. :)

[Xi Han, 2015/01/19 22:40:05]

Sounds good:)

 
   DISALLOW_COPY_AND_ASSIGN(RequestContentScript);
 };