Adds a new class HttpCache::Writers for multiple cache transactions reading from the network.

net/http/http_cache.h

Index: net/http/http_cache.h
diff --git a/net/http/http_cache.h b/net/http/http_cache.h
index e420c7244204874988b4908149bf51a2bd8697a3..d3a0a4b0853a0ca80abf848c04135cf11930da15 100644
--- a/net/http/http_cache.h
+++ b/net/http/http_cache.h
@@ -246,6 +246,9 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
   class QuicServerInfoFactoryAdaptor;
   class Transaction;
   class WorkItem;
+  class Writers;
+  friend class WritersTest;  // To access ActiveEntry in the test class.
+  friend class MockHttpCacheTransaction;
   friend class Transaction;
   friend class ViewCacheHelper;
   struct PendingOp;  // Info for an entry under construction.
@@ -424,6 +427,11 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
   // Called when the transaction has finished reading from this entry.
   void DoneReadingFromEntry(ActiveEntry* entry, Transaction* transaction);
 
+  // Called when the transaction has received a non-matching response to
+  // validation and it's not the transaction responsible for writing the
+  // response body.
+  void DoomEntryValidationNoMatch(ActiveEntry* entry);
+
   // Removes and returns all queued transactions in |entry| in FIFO order. This
   // includes transactions that have completed the headers phase and those that
   // have not been added to the entry yet in that order. |list| is the output
@@ -431,8 +439,7 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory {
   void RemoveAllQueuedTransactions(ActiveEntry* entry, TransactionList* list);
 
   // Processes either writer's failure to write response body or
-  // headers_transactions's failure to write headers. Also invoked when headers
-  // transaction's validation result is not a match.
+  // headers_transactions's failure to write headers.
   void ProcessEntryFailure(ActiveEntry* entry, Transaction* transaction);
 
   // Restarts headers_transaction and done_headers_queue transactions.