Change the API of disk_cache::CreateCacheBackend to use scoped_ptr

net/disk_cache/entry_unittest.cc

Index: net/disk_cache/entry_unittest.cc
diff --git a/net/disk_cache/entry_unittest.cc b/net/disk_cache/entry_unittest.cc
index f54cec0f770e72379dd6f366b8deca703fa76b83..bbf1e433bf3c4804b89e214a4a10bed3167737db 100644
--- a/net/disk_cache/entry_unittest.cc
+++ b/net/disk_cache/entry_unittest.cc
@@ -2025,17 +2025,17 @@ TEST_F(DiskCacheEntryTest, MemoryOnlyDoomSparseEntry) {
 // way to simulate a race is to execute what we want on the callback.
 class SparseTestCompletionCallback: public net::TestCompletionCallback {
  public:
-  explicit SparseTestCompletionCallback(disk_cache::Backend* cache)
+  explicit SparseTestCompletionCallback(scoped_ptr<disk_cache::Backend>* cache)

[rvargas (doing something else), 2013/07/26 21:05:01]

nit: this is kind of ugly :(. The argument suggest transfer of ownership (in
fact as an out argument), but there is no real transfer of ownership even though
this class will delete the cache later on.

Isn't it better to leave this class using plain pointers and make the test do
the ugly dance of coping with the cache being deleted at some point by someone
else?. At least while reading the test what's going on will be explicit.

[qsr, 2013/07/29 08:26:28]

 Given that this is a pointer to the scoped_ptr, and not a scoped_ptr, this is
not really a transfer of ownership... But I'm fine changing this if you prefer.

 Given what this class is doing, everything is ugly. I changed it by really
passing ownership of the backend to this class, and just keeping a pointer to it
beforehand. Is that fine with you?

       : cache_(cache) {
   }
 
  private:
   virtual void SetResult(int result) OVERRIDE {
-    delete cache_;
+    cache_->reset();
     TestCompletionCallback::SetResult(result);
   }
 
-  disk_cache::Backend* cache_;
+  scoped_ptr<disk_cache::Backend>* cache_;
   DISALLOW_COPY_AND_ASSIGN(SparseTestCompletionCallback);
 };
 
@@ -2063,13 +2063,10 @@ TEST_F(DiskCacheEntryTest, DoomSparseEntry2) {
   EXPECT_EQ(9, cache_->GetEntryCount());
 
   entry->Close();
-  SparseTestCompletionCallback cb(cache_);
+  SparseTestCompletionCallback cb(&cache_);
   int rv = cache_->DoomEntry(key, cb.callback());
   EXPECT_EQ(net::ERR_IO_PENDING, rv);
   EXPECT_EQ(net::OK, cb.WaitForResult());
-
-  // TearDown will attempt to delete the cache_.
-  cache_ = NULL;
 }
 
 void DiskCacheEntryTest::PartialSparseEntry() {