Support serial number requests in variations service.

BUG=140073
TEST=manual using inserted logging

Review URL: https://chromiumcodereview.appspot.com/10828106

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@149979 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/metrics/variations_service.cc

@@ -98,12 +98,15 @@ GURL GetVariationsServerURL() {
 }  // namespace
 
 VariationsService::VariationsService()
-    : variations_server_url_(GetVariationsServerURL()) {
+    : variations_server_url_(GetVariationsServerURL()),
+      create_trials_from_seed_called_(false) {
 }
 
 VariationsService::~VariationsService() {}
 
 bool VariationsService::CreateTrialsFromSeed(PrefService* local_prefs) {
+  create_trials_from_seed_called_ = true;
+
   TrialsSeed seed;
   if (!LoadTrialsSeedFromPref(local_prefs, &seed))
     return false;
@@ -132,6 +135,10 @@ bool VariationsService::CreateTrialsFromSeed(PrefService* local_prefs) {
 void VariationsService::StartRepeatedVariationsSeedFetch() {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
+  // Check that |CreateTrialsFromSeed| was called, which is necessary to
+  // retrieve the serial number that will be sent to the server.
+  DCHECK(create_trials_from_seed_called_);
+
   // Perform the first fetch.
   FetchVariationsSeed();
 
@@ -157,6 +164,10 @@ void VariationsService::FetchVariationsSeed() {
   pending_seed_request_->SetRequestContext(
       g_browser_process->system_request_context());
   pending_seed_request_->SetMaxRetries(kMaxRetrySeedFetch);
+  if (!variations_serial_number_.empty()) {
+    pending_seed_request_->AddExtraRequestHeader("If-Match:" +
+                                                 variations_serial_number_);
+  }
   pending_seed_request_->Start();
 }
 
@@ -169,9 +180,10 @@ void VariationsService::OnURLFetchComplete(const net::URLFetcher* source) {
     DVLOG(1) << "Variations server request failed.";
     return;
   }
+
   if (request->GetResponseCode() != 200) {
     DVLOG(1) << "Variations server request returned non-200 response code: "
-            << request->GetResponseCode();
+             << request->GetResponseCode();
     return;
   }
 
@@ -214,6 +226,7 @@ bool VariationsService::StoreSeedData(const std::string& seed_data,
   local_prefs->SetString(prefs::kVariationsSeed, base64_seed_data);
   local_prefs->SetInt64(prefs::kVariationsSeedDate,
                         seed_date.ToInternalValue());
+  variations_serial_number_ = seed.serial_number();
   return true;
 }
 
@@ -415,6 +428,7 @@ bool VariationsService::LoadTrialsSeedFromPref(PrefService* local_prefs,
     local_prefs->ClearPref(prefs::kVariationsSeed);
     return false;
   }
+  variations_serial_number_ = seed->serial_number();
   return true;
 }
 

chrome/browser/metrics/variations_service.h

@@ -40,7 +40,8 @@ class VariationsService : public net::URLFetcherDelegate {
   bool CreateTrialsFromSeed(PrefService* local_prefs);
 
   // Calls FetchVariationsSeed once and repeats this periodically. See
-  // implementation for details on the period.
+  // implementation for details on the period. Must be called after
+  // |CreateTrialsFromSeed|.
   void StartRepeatedVariationsSeedFetch();
 
   // Starts the fetching process once, where |OnURLFetchComplete| is called with
@@ -127,9 +128,16 @@ class VariationsService : public net::URLFetcherDelegate {
   // The URL to use for querying the variations server.
   GURL variations_server_url_;
 
+  // Cached serial number from the most recently fetched variations seed.
+  std::string variations_serial_number_;
+
+  // Tracks whether |CreateTrialsFromSeed| has been called, to ensure that
+  // it gets called prior to |StartRepeatedVariationsSeedFetch|.
+  bool create_trials_from_seed_called_;
+
   // The timer used to repeatedly ping the server. Keep this as an instance
   // member so if VariationsService goes out of scope, the timer is
-  // automatically cancelled.
+  // automatically canceled.
   base::RepeatingTimer<VariationsService> timer_;
 };