base::Bind: Implement a 1-arity CancelableCallback and use this to implement

chrome/browser/renderer_host/offline_resource_handler.cc

Index: chrome/browser/renderer_host/offline_resource_handler.cc
diff --git a/chrome/browser/renderer_host/offline_resource_handler.cc b/chrome/browser/renderer_host/offline_resource_handler.cc
index 536e27cc800110f3a89d906560d34cb4b2e9f054..4d2b9ebea77840fe51a79200184d765314421206 100644
--- a/chrome/browser/renderer_host/offline_resource_handler.cc
+++ b/chrome/browser/renderer_host/offline_resource_handler.cc
@@ -45,7 +45,7 @@ OfflineResourceHandler::OfflineResourceHandler(
 
 OfflineResourceHandler::~OfflineResourceHandler() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  DCHECK(!appcache_completion_callback_.get());
+  DCHECK(appcache_completion_callback_.IsCancelled());
 }
 
 bool OfflineResourceHandler::OnUploadProgress(int request_id,
@@ -77,26 +77,22 @@ bool OfflineResourceHandler::OnResponseCompleted(
 }
 
 void OfflineResourceHandler::OnRequestClosed() {
-  if (appcache_completion_callback_) {
-    appcache_completion_callback_->Cancel();
-    appcache_completion_callback_.release();
+  if (!appcache_completion_callback_.IsCancelled()) {
+    appcache_completion_callback_.Cancel();
     Release();  // Balanced with OnWillStart
   }
+
   next_handler_->OnRequestClosed();
 }
 
 void OfflineResourceHandler::OnCanHandleOfflineComplete(int rv) {
-  CHECK(appcache_completion_callback_);

[awong, 2011/11/30 00:52:55]

Do we no longer need an equivalent check?  Maybe
CHECK(appcache_completion_callback_.IsCancelled()) and then reset?

[James Hawkins, 2011/11/30 01:44:58]

IMO the check is superfluous (we're in the callback afterall.  I'll add the
Cancel though.

-  appcache_completion_callback_ = NULL;
   if (deferred_request_id_ == -1) {
-    LOG(WARNING) << "OnCanHandleOfflineComplete called after completion: "
-                 << " this=" << this;
-    NOTREACHED();
-    return;
+    DLOG(FATAL) << "OnCanHandleOfflineComplete called after completion: "
+                << " this=" << this;

[awong, 2011/11/30 00:52:55]

You need a return; still.

[James Hawkins, 2011/11/30 01:44:58]

Done.

   }
+
   if (rv == net::OK) {
     Resume();
-    Release();  // Balanced with OnWillStart
   } else {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
@@ -112,14 +108,13 @@ bool OfflineResourceHandler::OnWillStart(int request_id,
     deferred_url_ = url;
     DVLOG(1) << "OnWillStart: this=" << this << ", request id=" << request_id
              << ", url=" << url;
-    AddRef();  //  Balanced with OnCanHandleOfflineComplete
-    DCHECK(!appcache_completion_callback_);
-    appcache_completion_callback_ =
-        new net::CancelableOldCompletionCallback<OfflineResourceHandler>(
-            this, &OfflineResourceHandler::OnCanHandleOfflineComplete);
+
+    DCHECK(appcache_completion_callback_.IsCancelled());

[awong, 2011/11/30 00:52:55]

I think you still need to retain the manual AddRef() and Relaese() calls.  As
is, I think we introduce a refcount cycle on this since
appcache_completion_callback_ takes a reference onto this.

[James Hawkins, 2011/11/30 01:44:58]

Per-offline, made the callback own |this|.

+    appcache_completion_callback_.Reset(
+        base::Bind(&OfflineResourceHandler::OnCanHandleOfflineComplete, this));
     appcache_service_->CanHandleMainResourceOffline(
         url, request_->first_party_for_cookies(),
-        appcache_completion_callback_);
+        appcache_completion_callback_.callback());
 
     *defer = true;
     return true;