Remove dead code in FrameSelection.

Remove the following dead code:
 - FrameSelection::copyTypingStyle
 - FrameSelection::isAll
 - FrameSelection::moveTo(const Position&, const Position&, EAffinity, EUserTriggered)
 - FrameSelection::moveTo(const Range*, EAffinity, EUserTriggered)
 - FrameSelection::paintDragCaret declaration
 - FrameSelection::setBase(const Position&, EAffinity, EUserTriggered)
 - FrameSelection::setExtent(const Position&, EAffinity, EUserTriggered)
 - FrameSelection::shouldShowBlockCursor

BUG=none
TEST=none

Review URL: https://codereview.chromium.org/141403002

git-svn-id: svn://svn.chromium.org/blink/trunk@165272 bbb929c8-8fbe-4397-9dbb-9b2b20218538