Determine prevalence of cache-control: no-store in main frame resources.

net/http/http_cache_transaction.cc

 // 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.
 
 #include "net/http/http_cache_transaction.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 99 matching lines @@
   };
   VaryType vary = VARY_NOT_PRESENT;
   if (response->vary_data.is_valid()) {
     vary = VARY_OTHER;
     if (response->headers->HasHeaderValue("vary", "user-agent"))
       vary = VARY_UA;
   }
   UMA_HISTOGRAM_ENUMERATION("HttpCache.Vary", vary, VARY_MAX);
 }
 
+void RecordNoStoreHeaderHistogram(int load_flags,
+                                  const net::HttpResponseInfo* response) {
+  if (load_flags & net::LOAD_MAIN_FRAME) {
+    UMA_HISTOGRAM_BOOLEAN(
+        "Net.MainFrameNoStore",
+        response->headers->HasHeaderValue("cache-control", "no-store"));
+  }
+}
+
 }  // namespace
 
 namespace net {
 
 struct HeaderNameAndValue {
   const char* name;
   const char* value;
 };
 
 // If the request includes one of these request headers, then avoid caching
@@ skipping 890 matching lines @@
     entry_ = NULL;
     mode_ = NONE;
   }
 
   if (request_->method == "POST" &&
       NonErrorResponse(new_response->headers->response_code())) {
     cache_->DoomMainEntryForUrl(request_->url);
   }
 
   RecordVaryHeaderHistogram(new_response);
+  RecordNoStoreHeaderHistogram(request_->load_flags, new_response);
 
   if (new_response_->headers->response_code() == 416 &&
       (request_->method == "GET" || request_->method == "POST")) {
     // If there is an ective entry it may be destroyed with this transaction.
     response_ = *new_response_;
     return OK;
   }
 
   // Are we expecting a response to a conditional query?
   if (mode_ == READ_WRITE || mode_ == UPDATE) {
@@ skipping 1480 matching lines @@
     default:
       NOTREACHED();
   }
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
 }  // namespace net