Split HttpCache miss tracking by Open and Create

net/http/http_cache_transaction.cc

Index: net/http/http_cache_transaction.cc
diff --git a/net/http/http_cache_transaction.cc b/net/http/http_cache_transaction.cc
index 3f59af233a994f6778fe380f0ba341a287e7b89d..02d1796bb8568bba34012df8d1a78c25f362585e 100644
--- a/net/http/http_cache_transaction.cc
+++ b/net/http/http_cache_transaction.cc
@@ -724,6 +724,7 @@ int HttpCache::Transaction::DoGetBackendComplete(int result) {
     if (effective_load_flags_ & LOAD_ONLY_FROM_CACHE) {
       mode_ = READ;
     } else if (effective_load_flags_ & LOAD_BYPASS_CACHE) {
+      UpdateTransactionPattern(PATTERN_NOT_COVERED);
       mode_ = WRITE;
     } else {
       mode_ = READ_WRITE;
@@ -960,6 +961,7 @@ int HttpCache::Transaction::DoOpenEntryComplete(int result) {
   }
 
   if (mode_ == READ_WRITE) {
+    miss_since_ = TimeTicks::Now();
     mode_ = WRITE;
     next_state_ = STATE_CREATE_ENTRY;
     return OK;
@@ -2491,6 +2493,9 @@ void HttpCache::Transaction::RecordHistograms() {
       UMA_HISTOGRAM_TIMES("HttpCache.BeforeSend.NotCached", before_send_time);
       UMA_HISTOGRAM_PERCENTAGE("HttpCache.PercentBeforeSend.NotCached",
                                before_send_percent);
+      DCHECK(!miss_since_.is_null());
+      TimeDelta before_miss_time = miss_since_ - first_cache_access_since_;
+      UMA_HISTOGRAM_TIMES("HttpCache.BeforeCreate.NotCached", before_miss_time);
       break;
     }
     case PATTERN_ENTRY_VALIDATED: {