Support optimistic Create and Write operations on the SimpleCache.

net/disk_cache/simple/simple_entry_impl.h

Index: net/disk_cache/simple/simple_entry_impl.h
diff --git a/net/disk_cache/simple/simple_entry_impl.h b/net/disk_cache/simple/simple_entry_impl.h
index 87eeccae810a508b1a9cdfe984f8375028d18ff2..fcaff7953d8afba868c15154222e45e7b84a6c8c 100644
--- a/net/disk_cache/simple/simple_entry_impl.h
+++ b/net/disk_cache/simple/simple_entry_impl.h
@@ -104,6 +104,10 @@ class SimpleEntryImpl : public Entry, public base::RefCounted<SimpleEntryImpl>,
     // IO is currently in flight, operations must wait for completion before
     // launching.
     STATE_IO_PENDING,
+
+    // A failure occurred in the current or previous operation. All operations
+    // after that must fail too.

[pasko-google - do not use, 2013/05/02 14:01:43]

this is not strictly true because we can still do optimistic creates, also Close
succeeds.

[felipeg, 2013/05/02 14:10:05]

No we can't do optimistic creates on a failed entry.
We must be in STATE_UNINITIALIZED.

About the close operation: That is true, but I didn't meant that.
Let me be more clear.

+    STATE_FAILURE,
   };
 
   virtual ~SimpleEntryImpl();
@@ -130,11 +134,10 @@ class SimpleEntryImpl : public Entry, public base::RefCounted<SimpleEntryImpl>,
   // the last reference.
   void RunNextOperationIfNeeded();
 
-  void OpenEntryInternal(Entry** entry,
-                         const CompletionCallback& callback);
+  void OpenEntryInternal(const CompletionCallback& callback, Entry** out_entry);

[gavinp, 2013/05/02 12:47:39]

This change of parameter ordering is a bit confusing; the order was the same as
in disk_cache::Backend, and now it's reversed. Why?

[felipeg, 2013/05/02 13:55:58]

Output parameters should come last.
That is not in the style guide but is a common practice.
Do you want me to change back ?

 
-  void CreateEntryInternal(Entry** entry,
-                           const CompletionCallback& callback);
+  void CreateEntryInternal(const CompletionCallback& callback,
+                           Entry** out_entry);
 
   void CloseInternal();