Use a Finch Experiment to control the Browser Blacklist

chrome/browser/chrome_elf_init_win.cc

Index: chrome/browser/chrome_elf_init_win.cc
diff --git a/chrome/browser/chrome_elf_init_win.cc b/chrome/browser/chrome_elf_init_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..672b0a3ebdaff2571545c72c3b7f9320c18e913d
--- /dev/null
+++ b/chrome/browser/chrome_elf_init_win.cc
@@ -0,0 +1,103 @@
+// Copyright 2014 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 "base/metrics/field_trial.h"
+#include "base/metrics/histogram.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/win/registry.h"
+#include "chrome/browser/chrome_elf_init_win.h"
+#include "chrome_elf/blacklist/blacklist.h"
+#include "version.h"  // NOLINT
+
+namespace {
+
+const char kBrowserBlacklistTrialName[] = "BrowserBlacklist";
+const char kBrowserBlacklistTrialEnabledGroupName[] = "Enabled";
+
+// This enum is used to define the buckets for an enumerated UMA histogram.
+// Hence,
+//   (a) existing enumerated constants should never be deleted or reordered, and
+//   (b) new constants should only be appended in front of
+//       BLACKLIST_SETUP_EVENT_MAX.
+enum BlacklistSetupEventType {
+  // The blacklist beacon has placed to enable the browser blacklisting.
+  BLACKLIST_SETUP_ENABLED = 0,
+
+  // The blacklist was successfully enabled.
+  BLACKLIST_SETUP_RAN_SUCCESSFULLY,
+
+  // The blacklist setup code failed to execute.
+  BLACKLIST_SETUP_FAILED,
+
+  // Always keep this at the end.
+  BLACKLIST_SETUP_EVENT_MAX,
+};
+
+void RecordBlacklistSetupEvent(BlacklistSetupEventType blacklist_setup_event) {
+  UMA_HISTOGRAM_ENUMERATION("Blacklist.Setup",
+                            blacklist_setup_event,
+                            BLACKLIST_SETUP_EVENT_MAX);
+}
+
+}  // namespace
+
+void InitializeChromeElf() {
+  if (base::FieldTrialList::FindFullName(kBrowserBlacklistTrialName) ==
+      kBrowserBlacklistTrialEnabledGroupName) {
+    BrowserBlacklistBeaconSetup();
+  } else {
+    // Disable the blacklist for all future runs by removing the beacon.
+    base::win::RegKey blacklist_registry_key(HKEY_CURRENT_USER);
+    blacklist_registry_key.DeleteKey(blacklist::kRegistryBeaconPath);
+  }
+}
+
+void BrowserBlacklistBeaconSetup() {
+  base::win::RegKey blacklist_registry_key(HKEY_CURRENT_USER,
+                                           blacklist::kRegistryBeaconPath,
+                                           KEY_QUERY_VALUE | KEY_SET_VALUE);
+
+  // Find the last recorded blacklist version.
+  base::string16 blacklist_version;
+  blacklist_registry_key.ReadValue(blacklist::kBeaconVersion,
+                                   &blacklist_version);
+
+  if (blacklist_version != TEXT(CHROME_VERSION_STRING)) {
+    // The blacklist hasn't run for this version yet, so enable it.
+    LONG set_version = blacklist_registry_key.WriteValue(
+        blacklist::kBeaconVersion,
+        TEXT(CHROME_VERSION_STRING));
+
+    LONG set_state = blacklist_registry_key.WriteValue(
+        blacklist::kBeaconState,
+        blacklist::BLACKLIST_ENABLED);
+
+    // Only report the blacklist as getting setup when both registry writes
+    // succeed, since otherwise the blacklist wasn't properly setup.
+    if (set_version == ERROR_SUCCESS && set_state == ERROR_SUCCESS)
+      RecordBlacklistSetupEvent(BLACKLIST_SETUP_ENABLED);
+
+    // Don't try to record if the blacklist setup succeeded or failed in the
+    // run since it could have been from either this version or the previous
+    // version (since crashes occur before we set the version in the registry).
+  } else {
+    // The blacklist version didn't change, so record the results of the
+    // latest setup.
+    DWORD blacklist_state = blacklist::BLACKLIST_STATE_MAX;
+    blacklist_registry_key.ReadValueDW(blacklist::kBeaconState,
+                                       &blacklist_state);
+
+    // Record the results of the latest blacklist setup.
+    if (blacklist_state == blacklist::BLACKLIST_ENABLED) {
+      RecordBlacklistSetupEvent(BLACKLIST_SETUP_RAN_SUCCESSFULLY);
+    } else if (blacklist_state == blacklist::BLACKLIST_SETUP_RUNNING) {
+      RecordBlacklistSetupEvent(BLACKLIST_SETUP_FAILED);
+
+      // Since the setup failed, mark the blacklist as disabled so we don't
+      // try it again for this version.
+      blacklist_registry_key.WriteValue(blacklist::kBeaconState,
+                                        blacklist::BLACKLIST_DISABLED);
+    }
+  }
+}