Fixes the cache lock issue.

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 2aae2fcf27e1cc0aed6fcbbe3b73eb3c3d293708..f4e467594842bb03fac3e2fb9cb09cb563416879 100644
--- a/net/http/http_cache.h
+++ b/net/http/http_cache.h
@@ -19,6 +19,7 @@
 #include <memory>
 #include <string>
 #include <unordered_map>
+#include <unordered_set>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
@@ -202,7 +203,7 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
 
   // HttpTransactionFactory implementation:
   int CreateTransaction(RequestPriority priority,
-                        std::unique_ptr<HttpTransaction>* trans) override;
+                        std::unique_ptr<HttpTransaction>* transaction) override;
   HttpCache* GetCache() override;
   HttpNetworkSession* GetSession() override;
 
@@ -229,15 +230,17 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
     kNumCacheEntryDataIndices
   };
 
+  class DataAccess;
+  class SharedWriters;
+  class Transaction;
+  using TransactionList = std::list<Transaction*>;
+  using TransactionSet = std::unordered_set<Transaction*>;
   class MetadataWriter;
   class QuicServerInfoFactoryAdaptor;
-  class Transaction;
   class WorkItem;
-  friend class Transaction;
   friend class ViewCacheHelper;
   struct PendingOp;  // Info for an entry under construction.
 
-  typedef std::list<Transaction*> TransactionList;
   typedef std::list<std::unique_ptr<WorkItem>> WorkItemList;
 
   struct ActiveEntry {
@@ -245,8 +248,10 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
     ~ActiveEntry();
 
     disk_cache::Entry* disk_entry;
+    // Either writer or shared_writers will be non-null at any point in time.
     Transaction*       writer;
-    TransactionList    readers;
+    std::unique_ptr<SharedWriters> shared_writers;
+    TransactionSet readers;
     TransactionList    pending_queue;
     bool               will_process_pending_queue;
     bool               doomed;
@@ -302,7 +307,8 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
   // cache entry.
   ActiveEntry* ActivateEntry(disk_cache::Entry* disk_entry);
 
-  // Deletes an ActiveEntry.
+  // Deletes an ActiveEntry. Expects writer to be nullptr and containers to be
+  // empty: shared_writers, pending_queue and readers.
   void DeactivateEntry(ActiveEntry* entry);
 
   // Deletes an ActiveEntry using an exhaustive search.
@@ -392,6 +398,50 @@ class NET_EXPORT HttpCache : public HttpTransactionFactory,
   // Processes the backend creation notification.
   void OnBackendCreated(int result, PendingOp* pending_op);
 
+  // Destroys the entry and any pending queue transactions' callbacks are
+  // invoked with ERR_CACHE_RACE that restarts their state machine.
+  void DestroyEntryRestartPendingQueue(ActiveEntry* entry);
+
+  // Dooms the entry and any pending queue transactions' callbacks are
+  // invoked with ERR_CACHE_RACE that restarts their state machine.
+  void DoomEntryRestartPendingQueue(const std::string& key, ActiveEntry* entry);
+
+  // Writes response info to entry.
+  int WriteResponseInfo(ActiveEntry* entry,
+                        const HttpResponseInfo* response,
+                        CompletionCallback& callback,
+                        bool truncated,
+                        int* io_buf_len);
+
+  // Checks if the response is completed based on content length.
+  bool IsResponseCompleted(const ActiveEntry* entry,
+                           const HttpResponseInfo* response);
+
+  // Returns true if we should bother attempting to resume this request if it is
+  // aborted while in progress. If |has_data| is true, the size of the stored
+  // data is considered for the result.
+  bool CanResumeEntry(bool has_data,
+                      const std::string& method,
+                      const HttpResponseInfo* response,
+                      ActiveEntry* entry);
+
+  // Response data completely written to the cache successfully, or
+  // Response data could not be written to the cache successfully, or
+  // Response data could not be read from the network successfully.
+  // Success is true if the entry was marked as truncated successfully.
+  // destroyed is set to true when the calling SharedWiters object is reset.
+  void ResponseDoneSharedWriters(ActiveEntry* entry,
+                                 bool success,
+                                 bool* destroyed);
+
+  // Resets SharedWriters if entry contains an empty SharedWriters object and
+  // calls ProcessPendingQueue.
+  void ResetSharedWritersProcessPendingQueue(ActiveEntry* entry);
+  void ResetSharedWriters(ActiveEntry* entry);
+
+  void RemovedSharedWriterTransaction(Transaction* transaction,
+                                      ActiveEntry* entry);
+
   // Variables ----------------------------------------------------------------
 
   NetLog* net_log_;