Attach (recommended) or Link to PDF file here:
https://bitcoin.org/bitcoin.pdf

Configuration:
- Web browser and its version: all
- Operating system and its version: all
- PDF.js version: tested with 2.9.11, but most likely all versions
- Is a browser extension: no

Steps to reproduce the problem:
1. Type "a purely" (single space between "a" and "purely") - doesn't find anything
2. Type "a  purely" (two spaces between "a" and "purely") - finds the phrase

Sometimes even 3 spaces are necessary.

What is the expected behavior? (add screenshot)
![Screenshot from 2021-04-08 13-00-03](https://user-images.githubusercontent.com/6362989/114008903-57639a00-986b-11eb-903a-92bbebbd922b.png)

What went wrong? (add screenshot)
![Screenshot from 2021-04-08 13-01-53](https://user-images.githubusercontent.com/6362989/114008810-44e96080-986b-11eb-8232-f58a62ed7899.png)

This affects many PDFs because justify alignment is common enough.
Util,
} from "../shared/util.js";
/**
 * Text layer render parameters.
 *
 * @typedef {Object} TextLayerRenderParameters
 * @property {import("./api").TextContent} [textContent] - Text content to
 *   render (the object is returned by the page's `getTextContent` method).
 * @property {ReadableStream} [textContentStream] - Text content stream to
 *   render (the stream is returned by the page's `streamTextContent` method).
 * @property {HTMLElement} container - HTML element that will contain text runs.
 * @property {import("./display_utils").PageViewport} viewport - The target
 *   viewport to properly layout the text runs.
 * @property {Array<HTMLElement>} [textDivs] - HTML elements that are correspond
 *   to the text items of the textContent input. This is output and shall be
 *   initially be set to empty array.
 * @property {Array<string>} [textContentItemsStr] - Strings that correspond to
 *    the `str` property of the text items of textContent input. This is output
 *   and shall be initially be set to empty array.
 * @property {number} [timeout] - Delay in milliseconds before rendering of the
 *   text runs occurs.
 * @property {boolean} [enhanceTextSelection] - Whether to turn on the text
 *   selection enhancement.
 */
const MAX_TEXT_DIVS_TO_RENDER = 100000;
const DEFAULT_FONT_SIZE = 30;
const DEFAULT_FONT_ASCENT = 0.8;
const ascentCache = new Map();
const AllWhitespaceRegexp = /^\s+$/g;
function getAscent(fontFamily, ctx) {