HttpCache::Transaction layer allowing parallel validation

net/http/http_cache_transaction.h

Index: net/http/http_cache_transaction.h
diff --git a/net/http/http_cache_transaction.h b/net/http/http_cache_transaction.h
index 2d249c1eda028c6329ed2edc603bfc2f4064a082..286907f2a49453f5d87e129209cb0ea7f3f3d7a9 100644
--- a/net/http/http_cache_transaction.h
+++ b/net/http/http_cache_transaction.h
@@ -218,6 +218,8 @@ class HttpCache::Transaction : public HttpTransaction {
     STATE_PARTIAL_HEADERS_RECEIVED,
     STATE_CACHE_READ_METADATA,
     STATE_CACHE_READ_METADATA_COMPLETE,
+    STATE_WAIT_BEFORE_READ,
+    STATE_WAIT_BEFORE_READ_COMPLETE,
 
     // These states are entered from Read/AddTruncatedFlag.
     STATE_NETWORK_READ,
@@ -245,6 +247,7 @@ class HttpCache::Transaction : public HttpTransaction {
   // Runs the state transition loop. Resets and calls |callback_| on exit,
   // unless the return value is ERR_IO_PENDING.
   int DoLoop(int result);
+  int DoLoopImpl(int result);
 
   // Each of these methods corresponds to a State value.  If there is an
   // argument, the value corresponds to the return of the previous state or
@@ -284,6 +287,8 @@ class HttpCache::Transaction : public HttpTransaction {
   int DoTruncateCachedMetadata();
   int DoTruncateCachedMetadataComplete(int result);
   int DoPartialHeadersReceived();
+  int DoWaitBeforeRead();
+  int DoWaitBeforeReadComplete(int result);
   int DoCacheReadMetadata();
   int DoCacheReadMetadataComplete(int result);
   int DoNetworkRead();
@@ -463,6 +468,8 @@ class HttpCache::Transaction : public HttpTransaction {
   bool couldnt_conditionalize_request_;
   bool bypass_lock_for_test_;  // A test is exercising the cache lock.
   bool fail_conditionalization_for_test_;  // Fail ConditionalizeRequest.
+  // This transaction is responsible for writing the response
+  bool write_this_response_;

[jkarlin, 2017/03/07 16:45:42]

This variable seems unnecessary, it's only read in one place which could just as
easily check if it's the entry's writers.

   scoped_refptr<IOBuffer> read_buf_;
   int io_buf_len_;
   int read_offset_;