Add support for response header manipulation in Declarative WebRequest API

chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h

Index: chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h
diff --git a/chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h b/chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h
index 5187688ef425e06673cfaab20e96b937ed54d09b..d12e2fc325fbfe1cb2d33fefcee75247fac67a56 100644
--- a/chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h
+++ b/chrome/browser/extensions/api/declarative_webrequest/webrequest_rule.h
@@ -25,6 +25,7 @@ struct EventResponseDelta;
 }
 
 namespace net {
+class HttpResponseHeaders;
 class URLRequest;
 }
 
@@ -41,6 +42,13 @@ class WebRequestRule {
   typedef std::pair<ExtensionId, RuleId> GlobalRuleId;
   typedef int Priority;
 
+  // Container to pass additional information about requests that are not
+  // available in all request stages.
+  struct OptionalRequestData {
+    OptionalRequestData() : original_response_headers(NULL) {}
+    net::HttpResponseHeaders* original_response_headers;
+  };
+
   WebRequestRule(const GlobalRuleId& id,
                  base::Time extension_installation_time,
                  scoped_ptr<WebRequestConditionSet> conditions,
@@ -64,7 +72,8 @@ class WebRequestRule {
 
   std::list<LinkedPtrEventResponseDelta> CreateDeltas(
       net::URLRequest* request,
-      RequestStages request_stage) const;
+      RequestStages request_stage,
+      const OptionalRequestData& optional_request_data) const;
 
   // Returns the minimum priority of rules that may be evaluated after
   // this rule. Defaults to MAX_INT. Only valid if the conditions of this rule