Googletest export

| `IsEmpty()`             | `argument` is an empty string.                     |

PiperOrigin-RevId: 352880252

docs/gmock_cheat_sheet.md

@@ -329,6 +329,7 @@ The `argument` can be either a C string or a C++ string object:
 | `ContainsRegex(string)` | `argument` matches the given regular expression.   |
 | `EndsWith(suffix)`      | `argument` ends with string `suffix`.              |
 | `HasSubstr(string)`     | `argument` contains `string` as a sub-string.      |
+| `IsEmpty()`             | `argument` is an empty string.                     |
 | `MatchesRegex(string)`  | `argument` matches the given regular expression with the match starting at the first character and ending at the last character. |
 | `StartsWith(prefix)`    | `argument` starts with string `prefix`.            |
 | `StrCaseEq(string)`     | `argument` is equal to `string`, ignoring case.    |