Add fine grain tracing to HostResolverImpl.

This will help in diagnosing the "slow resolving host" bugs.

Users can now click an "Enable tracing" button on "chrome://net-internals/hostresolver".
This logs detailed information on the DNS requests flowing through the browser (when they were received, when they were posted to the thread pool, when they started running on the worker thread, etc...).

BUG=12754

Review URL: http://codereview.chromium.org/556094

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@37776 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 23 insertions, 1 deletions

diff --git a/net/base/host_resolver_impl.h b/net/base/host_resolver_impl.h
index 77f9020..f3684b8 100644
--- a/net/base/host_resolver_impl.h
+++ b/net/base/host_resolver_impl.h
@@ -86,7 +86,6 @@ class HostResolverImpl : public HostResolver,
   virtual void CancelRequest(RequestHandle req);
   virtual void AddObserver(HostResolver::Observer* observer);
   virtual void RemoveObserver(HostResolver::Observer* observer);
-  virtual HostCache* GetHostCache();
 
   // TODO(eroman): temp hack for http://crbug.com/15513
   virtual void Shutdown();
@@ -95,6 +94,22 @@ class HostResolverImpl : public HostResolver,
     default_address_family_ = address_family;
   }
 
+  virtual bool IsHostResolverImpl() { return true; }
+
+  // Returns the cache this resolver uses, or NULL if caching is disabled.
+  HostCache* cache() { return cache_.get(); }
+
+  // Clears the request trace log.
+  void ClearRequestsTrace();
+
+  // Starts/ends capturing requests to a trace log.
+  void EnableRequestsTracing(bool enable);
+
+  bool IsRequestsTracingEnabled() const;
+
+  // Returns a copy of the requests trace log, or NULL if there is none.
+  scoped_refptr<LoadLog> GetRequestsTrace();
+
   // Applies a set of constraints for requests that belong to the specified
   // pool. NOTE: Don't call this after requests have been already been started.
   //
@@ -114,6 +129,7 @@ class HostResolverImpl : public HostResolver,
   class Job;
   class JobPool;
   class Request;
+  class RequestsTrace;
   typedef std::vector<Request*> RequestsList;
   typedef HostCache::Key Key;
   typedef std::map<Key, scoped_refptr<Job> > JobMap;
@@ -206,6 +222,10 @@ class HostResolverImpl : public HostResolver,
   // Observers are the only consumers of this ID number.
   int next_request_id_;
 
+  // Monotonically increasing ID number to assign to the next job.
+  // The only consumer of this ID is the requests tracing code.
+  int next_job_id_;
+
   // The procedure to use for resolving host names. This will be NULL, except
   // in the case of unit-tests which inject custom host resolving behaviors.
   scoped_refptr<HostResolverProc> resolver_proc_;
@@ -218,6 +238,8 @@ class HostResolverImpl : public HostResolver,
 
   const scoped_refptr<NetworkChangeNotifier> network_change_notifier_;
 
+  scoped_refptr<RequestsTrace> requests_trace_;
+
   DISALLOW_COPY_AND_ASSIGN(HostResolverImpl);
 };