Improve example code for cancelable request -- pass consumer base class pointer in StartRequest as it is more general

Make a small optimization: passing an iterator in CancelRequestLocked rather than Handle can avoid a call to map::find()

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/650143

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@39708 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 14 insertions, 13 deletions

diff --git a/chrome/browser/cancelable_request.cc b/chrome/browser/cancelable_request.cc
index 1d20eca..85ab51a 100644
--- a/chrome/browser/cancelable_request.cc
+++ b/chrome/browser/cancelable_request.cc
@@ -15,7 +15,7 @@ CancelableRequestProvider::~CancelableRequestProvider() {
   // then the Profile is deleted.
   AutoLock lock(pending_request_lock_);
   while (!pending_requests_.empty())
-    CancelRequestLocked(pending_requests_.begin()->first);
+    CancelRequestLocked(pending_requests_.begin());
 }
 
 CancelableRequestProvider::Handle CancelableRequestProvider::AddRequest(
@@ -38,19 +38,20 @@ CancelableRequestProvider::Handle CancelableRequestProvider::AddRequest(
 
 void CancelableRequestProvider::CancelRequest(Handle handle) {
   AutoLock lock(pending_request_lock_);
-  CancelRequestLocked(handle);
+  CancelRequestLocked(pending_requests_.find(handle));
 }
 
-void CancelableRequestProvider::CancelRequestLocked(Handle handle) {
-  CancelableRequestMap::iterator i = pending_requests_.find(handle);
-  if (i == pending_requests_.end()) {
+void CancelableRequestProvider::CancelRequestLocked(
+    const CancelableRequestMap::iterator& item) {
+  pending_request_lock_.AssertAcquired();
+  if (item == pending_requests_.end()) {
     NOTREACHED() << "Trying to cancel an unknown request";
     return;
   }
 
-  i->second->consumer()->OnRequestRemoved(this, handle);
-  i->second->set_canceled();
-  pending_requests_.erase(i);
+  item->second->consumer()->OnRequestRemoved(this, item->first);
+  item->second->set_canceled();
+  pending_requests_.erase(item);
 }
 
 void CancelableRequestProvider::RequestCompleted(Handle handle) {
diff --git a/chrome/browser/cancelable_request.h b/chrome/browser/cancelable_request.h
index 2dc4b9b..28bc8ed 100644
--- a/chrome/browser/cancelable_request.h
+++ b/chrome/browser/cancelable_request.h
@@ -41,7 +41,7 @@
 //     typedef Callback1<int>::Type RequestCallbackType;
 //
 //     Handle StartRequest(int some_input1, int some_input2,
-//                         CancelableRequestConsumer* consumer,
+//                         CancelableRequestConsumerBase* consumer,
 //                         RequestCallbackType* callback) {
 //       scoped_refptr<CancelableRequest<RequestCallbackType> > request(
 //           new CancelableRequest<RequestCallbackType>(callback));
@@ -137,14 +137,14 @@ class CancelableRequestProvider {
   void RequestCompleted(Handle handle);
 
  private:
+  typedef std::map<Handle, scoped_refptr<CancelableRequestBase> >
+      CancelableRequestMap;
+
   // Only call this when you already have acquired pending_request_lock_.
-  void CancelRequestLocked(Handle handle);
+  void CancelRequestLocked(const CancelableRequestMap::iterator& item);
 
   friend class CancelableRequestBase;
 
-  typedef std::map<Handle, scoped_refptr<CancelableRequestBase> >
-      CancelableRequestMap;
-
   Lock pending_request_lock_;
 
   // Lists all outstanding requests. Protected by the |lock_|.