RFC: use some in-memory state in SimpleCache to quickly cache-miss some CantConditionalize cases

net/http/http_cache_transaction.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file declares HttpCache::Transaction, a private class of HttpCache so
 // it should only be included by http_cache.cc
 
 #ifndef NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 #define NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 
@@ skipping 157 matching lines @@
   int ResumeNetworkStart() override;
   void GetConnectionAttempts(ConnectionAttempts* out) const override;
 
   // Invoked when parallel validation cannot proceed due to response failure
   // and this transaction needs to be restarted.
   void SetValidatingCannotProceed();
 
   // Returns the estimate of dynamically allocated memory in bytes.
   size_t EstimateMemoryUsage() const;
 
+  // ### comment
+  bool MaybeRejectBasedOnMemoryEntryData(uint8_t in_memory_info);
+
  private:
   static const size_t kNumValidationHeaders = 2;
   // Helper struct to pair a header name with its value, for
   // headers used to validate cache entries.
   struct ValidationHeaders {
     ValidationHeaders() : initialized(false) {}
 
     std::string values[kNumValidationHeaders];
     bool initialized;
   };
@@ skipping 172 matching lines @@
   // Returns network error code.
   int RestartNetworkRequestWithAuth(const AuthCredentials& credentials);
 
   // Called to determine if we need to validate the cache entry before using it.
   bool RequiresValidation();
 
   // Called to make the request conditional (to ask the server if the cached
   // copy is valid).  Returns true if able to make the request conditional.
   bool ConditionalizeRequest();
 
+  // Determines if saved response permits conditionalization, and extracts
+  // etag/last-modified values. Only depends on response_.headers.
+  bool ResponseConditionalizable(std::string* etag_value,
+                                 std::string* last_modified_value);
+
   // Makes sure that a 206 response is expected.  Returns true on success.
   // On success, handling_206_ will be set to true if we are processing a
   // partial entry.
   bool ValidatePartialResponse();
 
   // Handles a response validation error by bypassing the cache.
   void IgnoreRangeRequest();
 
   // Fixes the response headers to match expectations for a HEAD request.
   void FixHeadersForHead();
@@ skipping 169 matching lines @@
   RestartInfo restart_info_;
 
   base::WeakPtrFactory<Transaction> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Transaction);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_TRANSACTION_H_