Re-land another subset of r18520.

This particular subset should be a no-op: It adds an unused interface method (OnResolutionCancelled), and an unused test (CancelObserver), and lastly renames Cancel --> MarkAsCanceled().
The code in "dns_global.cc" is also unused since it is unreachable.

The original code review that this belongs to is:<http://codereview.chromium.org/125171>. (BUG=14138)

The original was backed out because of a valgrind linux error (BUG=14218), so I am now re-landing in smaller chunks to identify where the problem resides.
Review URL: http://codereview.chromium.org/126253

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@18581 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 9 insertions, 4 deletions

diff --git a/net/base/host_resolver.h b/net/base/host_resolver.h
index 34c803f..6e2add7 100644
--- a/net/base/host_resolver.h
+++ b/net/base/host_resolver.h
@@ -106,13 +106,18 @@ class HostResolver {
 
     // Called at the start of HostResolver::Resolve(). |id| is a unique number
     // given to the request, so it can be matched up with a corresponding call
-    // to OnFinishResolutionWithStatus().
+    // to OnFinishResolutionWithStatus() or OnCancelResolution().
     virtual void OnStartResolution(int id, const RequestInfo& info) = 0;
 
     // Called on completion of request |id|. Note that if the request was
-    // cancelled, OnFinishResolutionWithStatus() will not be called.
+    // cancelled, OnCancelResolution() will be called instead.
     virtual void OnFinishResolutionWithStatus(int id, bool was_resolved,
                                               const RequestInfo& info) = 0;
+
+    // Called when request |id| has been cancelled. A request is "cancelled"
+    // if either the HostResolver is destroyed while a resolution is in
+    // progress, or HostResolver::CancelRequest() is called.
+    virtual void OnCancelResolution(int id, const RequestInfo& info) = 0;
   };
 
   // Creates a HostResolver that caches up to |max_cache_entries| for
@@ -175,11 +180,11 @@ class HostResolver {
   // Callback for when |job| has completed with |error| and |addrlist|.
   void OnJobComplete(Job* job, int error, const AddressList& addrlist);
 
-  // Notify all obsevers of the start of a resolve request.
+  // Notify all observers of the start of a resolve request.
   void NotifyObserversStartRequest(int request_id,
                                    const RequestInfo& info);
 
-  // Notify all obsevers of the completion of a resolve request.
+  // Notify all observers of the completion of a resolve request.
   void NotifyObserversFinishRequest(int request_id,
                                     const RequestInfo& info,
                                     int error);