Chrome seems to have a bug. When the user clicks "Copy image",
it adds 'UniformResourceLocatorW' mime data, which contains both,
image description and the URL separated by a newline. That looks
like a bug, though I'm not sure, because Microsoft doesn't specify
the format of this field in its document.

Firefox doesn't have this bug, because it uses CF_HDROP instead.

BUG:438426