net: Return LoadTiming information in the case of a cache hit

net/http/http_cache_transaction.cc

Index: net/http/http_cache_transaction.cc
===================================================================
--- net/http/http_cache_transaction.cc	(revision 199488)
+++ net/http/http_cache_transaction.cc	(working copy)
@@ -24,6 +24,7 @@
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/load_flags.h"
+#include "net/base/load_timing_info.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/upload_data_stream.h"
@@ -488,9 +489,21 @@
     LoadTimingInfo* load_timing_info) const {
   if (network_trans_)
     return network_trans_->GetLoadTimingInfo(load_timing_info);
-  // Don't modify |load_timing_info| when reading from the cache instead of the
-  // network.
-  return false;
+
+  if (last_network_trans_load_timing_) {
+    *load_timing_info = *last_network_trans_load_timing_;
+    return true;
+  }
+
+  if (first_cache_access_since_.is_null())
+    return false;
+
+  // If the cache entry was opened, return that time.
+  load_timing_info->send_start = first_cache_access_since_;
+  // This time doesn't make much sense when reading from the cache, so just use
+  // the same time as send_start.
+  load_timing_info->send_end = first_cache_access_since_;
+  return true;
 }
 
 void HttpCache::Transaction::SetPriority(RequestPriority priority) {
@@ -826,6 +839,9 @@
   if (rv != OK)
     return rv;
 
+  // Old load timing information, if any, is now obsolete.
+  last_network_trans_load_timing_.reset();
+
   ReportNetworkActionStart();
   next_state_ = STATE_SEND_REQUEST_COMPLETE;
   rv = network_trans_->Start(request_, io_callback_, net_log_);
@@ -1259,12 +1275,14 @@
     }
     // We no longer need the network transaction, so destroy it.
     final_upload_progress_ = network_trans_->GetUploadProgress();
+    CacheLoadTimingInformation();
     network_trans_.reset();
   } else if (entry_ && handling_206_ && truncated_ &&
              partial_->initial_validation()) {
     // We just finished the validation of a truncated entry, and the server
     // is willing to resume the operation. Now we go back and start serving
     // the first part to the user.
+    CacheLoadTimingInformation();
     network_trans_.reset();
     new_response_ = NULL;
     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
@@ -2319,6 +2337,7 @@
 
   if (result == 0) {
     // We need to move on to the next range.
+    CacheLoadTimingInformation();
     network_trans_.reset();
     next_state_ = STATE_START_PARTIAL_CACHE_VALIDATION;
   }
@@ -2561,4 +2580,14 @@
   return return_value;
 }
 
+void HttpCache::Transaction::CacheLoadTimingInformation() {
+  DCHECK(!last_network_trans_load_timing_);
+  last_network_trans_load_timing_.reset(new LoadTimingInfo());
+  bool result =
+      network_trans_->GetLoadTimingInfo(last_network_trans_load_timing_.get());
+  // This is only called after getting a response from the transaction, so it
+  // should have timing information.
+  DCHECK(result);
+}
+
 }  // namespace net