Move the Chrome Variations HTTP header helper file into c/b/metrics/variations, and fix up lock beh…

chrome/browser/chrome_metrics_helper.cc

Index: chrome/browser/chrome_metrics_helper.cc
diff --git a/chrome/browser/chrome_metrics_helper.cc b/chrome/browser/chrome_metrics_helper.cc
deleted file mode 100644
index 578f29952fd2a89a8b31e28b4bf0ae42c9051987..0000000000000000000000000000000000000000
--- a/chrome/browser/chrome_metrics_helper.cc
+++ /dev/null
@@ -1,134 +0,0 @@
-// 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 "chrome/browser/chrome_metrics_helper.h"
-
-#include "base/base64.h"
-#include "base/memory/singleton.h"
-#include "chrome/browser/google/google_util.h"
-#include "chrome/browser/profiles/profile.h"
-#include "chrome/browser/profiles/profile_io_data.h"
-#include "chrome/common/metrics/proto/chrome_experiments.pb.h"
-#include "chrome/common/metrics/variations/variations_util.h"
-#include "content/public/browser/browser_thread.h"
-#include "net/http/http_request_headers.h"
-
-using content::BrowserThread;
-
-ChromeMetricsHelper* ChromeMetricsHelper::GetInstance() {
-  return Singleton<ChromeMetricsHelper>::get();
-}
-
-void ChromeMetricsHelper::AppendHeaders(const GURL& url,
-                                        bool incognito,
-                                        bool uma_enabled,
-                                        net::HttpRequestHeaders* headers) {
-  // Note the criteria for attaching Chrome experiment headers:
-  // 1. We only transmit to *.google.<TLD> domains. NOTE that this use of
-  //    google_util helpers to check this does not guarantee that the URL is
-  //    Google-owned, only that it is of the form *.google.<TLD>. In the future
-  //    we may choose to reinforce this check.
-  // 2. Only transmit for non-Incognito profiles.
-  // 3. For the X-Chrome-UMA-Enabled bit, only set it if UMA is in fact enabled
-  //    for this install of Chrome.
-  // 4. For the X-Chrome-Variations, only include non-empty variation IDs.
-  if (incognito ||
-      !google_util::IsGoogleDomainUrl(url.spec(),
-                                      google_util::ALLOW_SUBDOMAIN,
-                                      google_util::ALLOW_NON_STANDARD_PORTS)) {
-    return;
-  }
-
-  if (uma_enabled)
-    headers->SetHeaderIfMissing("X-Chrome-UMA-Enabled", "1");
-
-  // Lazily initialize the header, if not already done, before attempting to
-  // transmit it.
-  InitVariationIDsCacheIfNeeded();
-  base::AutoLock scoped_lock(lock_);
-  if (!variation_ids_header_.empty())
-    headers->SetHeaderIfMissing("X-Chrome-Variations", variation_ids_header_);
-}
-
-ChromeMetricsHelper::ChromeMetricsHelper()
-    : variation_ids_cache_initialized_(false) {
-}
-
-ChromeMetricsHelper::~ChromeMetricsHelper() {
-}
-
-void ChromeMetricsHelper::OnFieldTrialGroupFinalized(
-    const std::string& trial_name,
-    const std::string& group_name) {
-  chrome_variations::VariationID new_id =
-      chrome_variations::GetGoogleVariationID(
-          chrome_variations::GOOGLE_WEB_PROPERTIES, trial_name, group_name);
-  if (new_id == chrome_variations::kEmptyID)
-    return;
-  base::AutoLock scoped_lock(lock_);
-  variation_ids_set_.insert(new_id);
-  UpdateVariationIDsHeaderValue();
-}
-
-void ChromeMetricsHelper::InitVariationIDsCacheIfNeeded() {
-  base::AutoLock scoped_lock(lock_);
-  if (variation_ids_cache_initialized_)
-    return;
-
-  // Register for additional cache updates. This is done first to avoid a race
-  // that could cause registered FieldTrials to be missed.
-  DCHECK(MessageLoop::current());
-  base::FieldTrialList::AddObserver(this);
-
-  base::FieldTrial::ActiveGroups initial_groups;
-  base::FieldTrialList::GetActiveFieldTrialGroups(&initial_groups);
-  for (base::FieldTrial::ActiveGroups::const_iterator it =
-       initial_groups.begin(); it != initial_groups.end(); ++it) {
-    const chrome_variations::VariationID id =
-        chrome_variations::GetGoogleVariationID(
-            chrome_variations::GOOGLE_WEB_PROPERTIES, it->trial_name,
-            it->group_name);
-    if (id != chrome_variations::kEmptyID)
-      variation_ids_set_.insert(id);
-  }
-  UpdateVariationIDsHeaderValue();
-
-  variation_ids_cache_initialized_ = true;
-}
-
-void ChromeMetricsHelper::UpdateVariationIDsHeaderValue() {
-  // The header value is a serialized protobuffer of Variation IDs which is
-  // base64 encoded before transmitting as a string.
-  if (variation_ids_set_.empty())
-    return;
-
-  // This is the bottleneck for the creation of the header, so validate the size
-  // here. Force a hard maximum on the ID count in case the Variations server
-  // returns too many IDs and DOSs receiving servers with large requests.
-  DCHECK_LE(variation_ids_set_.size(), 10U);
-  if (variation_ids_set_.size() > 20) {
-    variation_ids_header_.clear();
-    return;
-  }
-
-  metrics::ChromeVariations proto;
-  for (std::set<chrome_variations::VariationID>::const_iterator it =
-      variation_ids_set_.begin(); it != variation_ids_set_.end(); ++it)
-    proto.add_variation_id(*it);
-
-  std::string serialized;
-  proto.SerializeToString(&serialized);
-
-  std::string hashed;
-  if (base::Base64Encode(serialized, &hashed)) {
-    // If successful, swap the header value with the new one.
-    // Note that the list of IDs and the header could be temporarily out of sync
-    // if IDs are added as the header is recreated. The receiving servers are OK
-    // with such descrepancies.
-    variation_ids_header_ = hashed;
-  } else {
-    NOTREACHED() << "Failed to base64 encode Variation IDs value: "
-                 << serialized;
-  }
-}