Support individual Keychain item deletion

chrome/browser/keychain_mock_mac.cc

Index: chrome/browser/keychain_mock_mac.cc
diff --git a/chrome/browser/keychain_mock_mac.cc b/chrome/browser/keychain_mock_mac.cc
index a6bd5fdb9de40f115e2f82050f5f2bf95ca983c5..879ffdcd2eb11cb6592ef194bebb69b8efdf0fff 100644
--- a/chrome/browser/keychain_mock_mac.cc
+++ b/chrome/browser/keychain_mock_mac.cc
@@ -229,6 +229,16 @@ OSStatus MockKeychain::ItemFreeAttributesAndData(
   return noErr;
 }
 
+OSStatus MockKeychain::ItemDelete(SecKeychainItemRef itemRef) const {
+  unsigned int item_index = reinterpret_cast<unsigned int>(itemRef) - 1;
+  // The mock only supports deleting the last item.
+  if (item_index != item_count_ - 1) {
+    NOTIMPLEMENTED();
+  }
+  --item_count_;
+  return noErr;
+}
+
 OSStatus MockKeychain::SearchCreateFromAttributes(
     CFTypeRef keychainOrArray, SecItemClass itemClass,
     const SecKeychainAttributeList *attrList,