Clipboard should respect user-select style attribute

Clipboard 'copy/paste'data also contains the elements on which
user-select:none property has been applied.
But the visible selection do not highlights those portions.
The copy data should respect the user-select attribute.
Currently the clipboard copy paste data only depends upon
the selection done in the DOM tree.
This CL makes the clipbaord text to work with the
text property

Bug: 147490
Change-Id: I5ccc6ebce67e630d0eb9949e514da77f52a6ed42
Reviewed-on: https://chromium-review.googlesource.com/763032
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Commit-Queue: Tanvir Rizvi <tanvir.rizvi@samsung.com>
Cr-Commit-Position: refs/heads/master@{#516608}
6 files changed