mac: Expose keychain access frequency to Telemetry.

components/os_crypt/os_crypt_mac.mm

 // 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 "components/os_crypt/os_crypt.h"
 
 #include <CommonCrypto/CommonCryptor.h>  // for kCCBlockSizeAES128
 
 #include "base/command_line.h"
 #include "base/debug/leak_annotations.h"
@@ skipping 44 matching lines @@
   static bool mock_keychain_command_line_flag =
       CommandLine::ForCurrentProcess()->HasSwitch(
           os_crypt::switches::kUseMockKeychain);
 
   std::string password;
   if (use_mock_keychain || mock_keychain_command_line_flag) {
     // Through manual testing, each call to SecKeychainFindGenericPassword
     // takes 4.6ms with a SSD, 3 GHz Intel Xeon. On a slower processor with a
     // HDD, this probably takes 4x as long.
     base::SpinCpuMicroseconds(18400);
+    base::EmitAccessKeychainHistogram();
 
     password = "mock_password";
   } else {
     AppleKeychain keychain;
     KeychainPassword encryptor_password(keychain);
     password = encryptor_password.GetPassword();
   }
 
   // Subsequent code must guarantee that the correct key is cached before
   // returning.
@@ skipping 91 matching lines @@
   if (!encryptor.Decrypt(raw_ciphertext, plaintext))
     return false;
 
   return true;
 }
 
 void OSCrypt::UseMockKeychain(bool use_mock) {
   use_mock_keychain = use_mock;
 }