Use DVLOG for SelectionOwner::OnSelectionClear

This logging appears informational rather than indicative of an error,
so we switch to DVLOG, as preferred by the style guide, to avoid log
spam.

Bug: 850209
Change-Id: Icb4ff66d083b5650d4e54cba04125fc311126992
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615560
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Auto-Submit: Kevin McNee <mcnee@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841265}

ui/base/x/selection_owner.cc

@@ -164,7 +164,7 @@ void SelectionOwner::OnSelectionRequest(
 }
 
 void SelectionOwner::OnSelectionClear(const x11::SelectionClearEvent& event) {
-  DLOG(ERROR) << "SelectionClear";
+  DVLOG(1) << "SelectionClear";
 
   // TODO(erg): If we receive a SelectionClear event while we're handling data,
   // we need to delay clearing.