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, 21 insertions, 5 deletions

diff --git a/chrome/browser/net/dns_global.cc b/chrome/browser/net/dns_global.cc
index cf7145c..9e4c8f6 100644
--- a/chrome/browser/net/dns_global.cc
+++ b/chrome/browser/net/dns_global.cc
@@ -149,6 +149,9 @@ class PrefetchObserver : public net::HostResolver::Observer {
       int request_id,
       bool was_resolved,
       const net::HostResolver::RequestInfo& request_info);
+  virtual void OnCancelResolution(
+      int request_id,
+      const net::HostResolver::RequestInfo& request_info);
 
   static void DnsGetFirstResolutionsHtml(std::string* output);
   static void SaveStartupListAsPref(PrefService* local_state);
@@ -202,12 +205,9 @@ void PrefetchObserver::OnStartResolution(
 
   NavigatingTo(request_info.hostname());
 
-  // TODO(eroman): If the resolve request is cancelled, then
-  // OnFinishResolutionWithStatus will not be called, and |resolutions| will
-  // grow unbounded!
-  // http://crbug.com/14138
-
   AutoLock auto_lock(*lock);
+  // This entry will be deleted either by OnFinishResolutionWithStatus(), or
+  // by  OnCancelResolution().
   (*resolutions)[request_id] = navigation_info;
 }
 
@@ -240,6 +240,22 @@ void PrefetchObserver::OnFinishResolutionWithStatus(
   StartupListAppend(navigation_info);
 }
 
+void PrefetchObserver::OnCancelResolution(
+    int request_id,
+    const net::HostResolver::RequestInfo& request_info) {
+  if (request_info.is_speculative())
+    return;  // One of our own requests.
+
+  // Remove the entry from |resolutions| that was added by OnStartResolution().
+  AutoLock auto_lock(*lock);
+  ObservedResolutionMap::iterator it = resolutions->find(request_id);
+  if (resolutions->end() == it) {
+    DCHECK(false);
+    return;
+  }
+  resolutions->erase(it);
+}
+
 // static
 void PrefetchObserver::StartupListAppend(const DnsHostInfo& navigation_info) {
   if (!on_the_record_switch || NULL == dns_master)