Introduce VisiblePosition::isValid

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

Index: third_party/WebKit/Source/core/editing/FrameSelection.cpp
diff --git a/third_party/WebKit/Source/core/editing/FrameSelection.cpp b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
index ef1eecc7a537282cf0fe0d01daed5f527562c252..61653f2e4bb10791e9c466b62f9ad4886b742cbb 100644
--- a/third_party/WebKit/Source/core/editing/FrameSelection.cpp
+++ b/third_party/WebKit/Source/core/editing/FrameSelection.cpp
@@ -179,10 +179,8 @@ void FrameSelection::moveTo(const Position &pos, TextAffinity affinity)
 template <typename Strategy>
 static void adjustEndpointsAtBidiBoundary(VisiblePositionTemplate<Strategy>& visibleBase, VisiblePositionTemplate<Strategy>& visibleExtent)
 {
-    // TODO(xiaochengh): Replace it with |DCHECK(visibleBase.isValid())| and
-    // |DCHECK(visibleExtent.isValid())| once |VisiblePosition::isValid| is
-    // implemented.
-    DCHECK(visibleBase.isNull() || !visibleBase.deepEquivalent().document()->needsLayoutTreeUpdate());
+    DCHECK(visibleBase.isValid());
+    DCHECK(visibleExtent.isValid());
 
     RenderedPosition base(visibleBase);
     RenderedPosition extent(visibleExtent);