Make sure end position of selection to delete editable

Make sure end position of selection to delete editable

This patch makes sure DeleteSelectionCommand to work on both start and end
positions of selection to delete editable, by adjusting end position to last
editable position of highest editable root from start position and assertion
for start position.

Start position is editable when DeleteSelection command is invoked
document.execCommand. Newly added assertion for start position will catch
commands which call DeleteSelectionCommand with non-editable selection.

BUG=361935
TEST=LayoutTests/editing/deleting/delete-selection-with-non-editable-end-crash.html

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=175336

[yosin_UTC9, 2014-06-02 08:10:28]

Could you review this patch?
Thanks in advance.

Note: Failure of "  blink_android_compile_rel" isn't related to this patch.

[Yuta Kitamura, 2014-06-03 06:27:39]

lgtm

[yosin_UTC9, 2014-06-03 06:33:56]

The CQ bit was checked by yosin@chromium.org

[yosin_UTC9, 2014-06-03 06:34:13]

The CQ bit was checked by yosin@chromium.org

[commit-bot: I haz the power, 2014-06-03 06:34:22]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/yosin@chromium.org/303263006/1

[commit-bot: I haz the power, 2014-06-03 06:38:04]

Change committed as 175336