function checkContentIsDefaultImg(page, defaultImgUrl) {
  const content = page.getContent();

  for (let i = 0; i < content.length; i++) {
    const url = getImageUrl(content[i]);
    assertTrue(
        `img src should be ${defaultImgUrl} but is ${url}`,
        checkPathsEndWithSameFile(url, defaultImgUrl));
  }
}
Checks that the content of an emojipicker page is all images pointing to
the default img.
@param {!EmojiPalette} page The page of the picker to check
@param {string} defaultImgUrl The url of the default img
@suppress {missingProperties} "length" on vague type