Remove unneeded block selection calculation code

Remove unneeded block selection calculation code
https://bugs.webkit.org/show_bug.cgi?id=178889

Reviewed by Tim Horton.

Removing more block selection code. Much of this should have been removed
before, as the only things that were using these functions were removed in the
last patch. Also remove the code decided if you should move to block mode or not,
as the answer now is always NO.

* WebProcess/WebPage/WebPage.h:
* WebProcess/WebPage/ios/WebPageIOS.mm:
(WebKit::WebPage::updateSelectionWithTouches):
(WebKit::WebPage::rangeForBlockAtPoint): Deleted.
(WebKit::distanceBetweenRectsForPosition): Deleted.
(WebKit::rectsEssentiallyTheSame): Deleted.
(WebKit::unionDOMRanges): Deleted.
(WebKit::computeEdgeCenter): Deleted.
(WebKit::WebPage::expandedRangeFromHandle): Deleted.
(WebKit::WebPage::contractedRangeFromHandle): Deleted.
(WebKit::WebPage::computeExpandAndShrinkThresholdsForHandle): Deleted.
(WebKit::WebPage::switchToBlockSelectionAtPoint): Deleted.
(WebKit::WebPage::shouldSwitchToBlockModeForHandle): Deleted.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@224068 268f45cc-cd09-0410-ab3c-d52691b4dbfc