Attach (recommended) or Link to PDF file here:
[298865.pdf](https://github.com/mozilla/pdf.js/files/2753236/298865.pdf)


Configuration:
- Web browser and its version:chrome 71.0.3578.98
- Operating system and its version:mac os 10.12.6
- PDF.js version:I use online demo in github
- Is a browser extension:no

Steps to reproduce the problem:
1. search "中华" or "电力" or so on,the highlight position is not right

What is the expected behavior? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087378-7eff5100-178d-11e9-991a-005d77b82f31.png)

What went wrong? (add screenshot)
![image](https://user-images.githubusercontent.com/10000986/51087374-6ee77180-178d-11e9-9707-281924f95fd0.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):
https://mozilla.github.io/pdf.js/web/viewer.html
const renderTask = pdfPage.render({
        canvasContext: canvasAndCtx.context,
        canvasFactory: CanvasFactory,
        viewport,
      });
      expect(renderTask instanceof RenderTask).toEqual(true);
      
      renderTask.onContinue = function (cont) {
        waitSome(cont);
      };
      try {
        await pdfDoc.cleanup();
        
        expect(false).toEqual(true);
      } catch (reason) {
        expect(reason instanceof Error).toEqual(true);
        expect(reason.message).toEqual(
          "startCleanup: Page 1 is currently rendering."
        );
      }
      await renderTask.promise;
      CanvasFactory.destroy(canvasAndCtx);
      await loadingTask.destroy();
    });
    it("caches image resources at the document/page level as expected (issue 11878)", async function () {
      const { NUM_PAGES_THRESHOLD } = GlobalImageCache,
        EXPECTED_WIDTH = 2550,
        EXPECTED_HEIGHT = 3300;
      const loadingTask = getDocument(buildGetDocumentParams("issue11878.pdf"));
      const pdfDoc = await loadingTask.promise;