Update from https://crrev.com/312398

crypto/mock_apple_keychain.cc

Index: crypto/mock_apple_keychain.cc
diff --git a/crypto/mock_apple_keychain.cc b/crypto/mock_apple_keychain.cc
index 1ddfc8679461c6fddf320642405dc31f98643c0b..a1faa65382a788ff5d8ac81b21b9723b41fb537c 100644
--- a/crypto/mock_apple_keychain.cc
+++ b/crypto/mock_apple_keychain.cc
@@ -3,9 +3,23 @@
 // found in the LICENSE file.
 
 #include "base/logging.h"
+#include "base/metrics/histogram.h"
 #include "base/time/time.h"
 #include "crypto/mock_apple_keychain.h"
 
+namespace {
+
+// Adds an entry to a local histogram to indicate that the Apple Keychain would
+// have been accessed, if this class were not a mock of the Apple Keychain.
+void IncrementKeychainAccessHistogram() {
+  // This local histogram is accessed by Telemetry to track the number of times
+  // the keychain is accessed, since keychain access is known to be synchronous
+  // and slow.
+  LOCAL_HISTOGRAM_BOOLEAN("OSX.Keychain.Access", true);
+}
+
+}  // namespace
+
 namespace crypto {
 
 OSStatus MockAppleKeychain::FindGenericPassword(
@@ -17,6 +31,8 @@ OSStatus MockAppleKeychain::FindGenericPassword(
     UInt32* passwordLength,
     void** passwordData,
     SecKeychainItemRef* itemRef) const {
+  IncrementKeychainAccessHistogram();
+
   // When simulating |noErr|, return canned |passwordData| and
   // |passwordLength|.  Otherwise, just return given code.
   if (find_generic_result_ == noErr) {
@@ -48,6 +64,8 @@ OSStatus MockAppleKeychain::AddGenericPassword(
     UInt32 passwordLength,
     const void* passwordData,
     SecKeychainItemRef* itemRef) const {
+  IncrementKeychainAccessHistogram();
+
   called_add_generic_ = true;
 
   DCHECK_GT(passwordLength, 0U);
@@ -58,4 +76,9 @@ OSStatus MockAppleKeychain::AddGenericPassword(
   return noErr;
 }
 
+std::string MockAppleKeychain::GetEncryptionPassword() const {
+  IncrementKeychainAccessHistogram();
+  return "mock_password";
+}
+
 }  // namespace crypto