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

BUG=383394

Review URL: https://codereview.chromium.org/329723006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276651 0039d316-1c4b-4281-b951-d872f2087c98

net/http/http_cache_transaction.cc

@@ -117,6 +117,15 @@ void RecordVaryHeaderHistogram(const net::HttpResponseInfo* response) {
   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 {
@@ -1027,6 +1036,7 @@ int HttpCache::Transaction::DoSuccessfulSendRequest() {
   }
 
   RecordVaryHeaderHistogram(new_response);
+  RecordNoStoreHeaderHistogram(request_->load_flags, new_response);
 
   if (new_response_->headers->response_code() == 416 &&
       (request_->method == "GET" || request_->method == "POST")) {

tools/metrics/histograms/histograms.xml

@@ -13784,6 +13784,18 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.MainFrameNoStore" enum="MainFrameStorable">
+  <owner>jkarlin@chromium.org</owner>
+  <summary>
+    The distribution of storable vs &quot;cache-control: no-store&quot;
+    main-frame resources.
+
+    Counted after response headers have completed and before the content has
+    completed. Redirects are counted. All HTTP cache transactions are counted,
+    not just those that require the network.
+  </summary>
+</histogram>
+
 <histogram name="Net.MTPR_GetProxyForUrl_Thread_Wait_Time" units="milliseconds">
   <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
   <summary>
@@ -39031,6 +39043,11 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <int value="5" label="OTHER_DEVELOPER">Other Dev</int>
 </enum>
 
+<enum name="MainFrameStorable" type="int">
+  <int value="0" label="Storable"/>
+  <int value="1" label="cache-control: no-store"/>
+</enum>
+
 <enum name="ManagedUserPasswordChange" type="int">
   <int value="0" label="OK_MANAGER">Changed in manager session</int>
   <int value="1" label="OK_MANGED">Changed in supervised user session</int>