Refactor VisibleSelectionTemplate::Validate()

This patch changes VisibleSelectionTemplate::Validate() to use early-return
for improving readability.

Change-Id: If1395322fd0fea262af37c9840c0976439f78cef
Reviewed-on: https://chromium-review.googlesource.com/563220Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485187}

third_party/WebKit/Source/core/editing/VisibleSelection.cpp

@@ -478,7 +478,9 @@ void VisibleSelectionTemplate<Strategy>::Validate(TextGranularity granularity) {
   AdjustSelectionToAvoidCrossingEditingBoundaries();
   UpdateSelectionType();
 
-  if (GetSelectionType() == kRangeSelection) {
+  if (GetSelectionType() != kRangeSelection)
+    return;
+
   // "Constrain" the selection to be the smallest equivalent range of
   // nodes. This is a somewhat arbitrary choice, but experience shows that
   // it is useful to make to make the selection "canonical" (if only for
@@ -490,7 +492,6 @@ void VisibleSelectionTemplate<Strategy>::Validate(TextGranularity granularity) {
   // |deepEquivalent()|s above)?
   start_ = MostForwardCaretPosition(start_);
   end_ = MostBackwardCaretPosition(end_);
-  }
 }
 
 template <typename Strategy>