Use default value of is_directional_ in WebLocalFrameImpl

WebLocalFrameImpl sets is_directional_ value to false
explicitly for building SelectionTemplate.
By default the is_directional_ value is false in
SelectionTemplate so we don't need to explicitly set.

Bug: 740804
Change-Id: I8f332d441b0265a230240fec30e892c4d55d4776
Reviewed-on: https://chromium-review.googlesource.com/765751Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Tanvir Rizvi <tanvir.rizvi@samsung.com>
Cr-Commit-Position: refs/heads/master@{#516329}

third_party/WebKit/Source/core/frame/WebLocalFrameImpl.cpp

@@ -1200,7 +1200,6 @@ void WebLocalFrameImpl::SelectRange(
       SelectionInDOMTree::Builder()
           .SetBaseAndExtent(range)
           .SetAffinity(TextAffinity::kDefault)
-          .SetIsDirectional(false)
           .Build(),
       SetSelectionOptions::Builder()
           .SetShouldShowHandle(show_handles)