docCommentTemplate returns "No content available" for ES5 method

[mjbvz]

From microsoft/vscode#60335

TypeScript Version: 3.2.0-dev.20181006

Search Terms:

• jsdoc
• docCommentTemplate

Code
For the javascript:

/** */
MyClass.prototype.myFunction = function (param1, param2) {
};

Request a docCommentTemplate at the | in /**| */

Bug:
No content available returned.

[Trace  - 11:44:31 AM] Sending request: docCommentTemplate (13). Response expected: yes. Current queue length: 0
Arguments: {
    "file": "/Users/matb/projects/san/b.js",
    "line": 1,
    "offset": 4
}
[Trace  - 11:44:31 AM] Response received: docCommentTemplate (13). Request took 2 ms. Success: false . Message: No content available.

This is a regression from TS 3.0.

We do return the expected response for the case:

/** */
function  foo(param1, param2) {
};

[sandersn]

This works in 3.5. Adding a test with #31477 to make sure it stays working.