wptserve: Import the latest revision of wptserve-related files.

third_party/WebKit/Tools/Scripts/webkitpy/thirdparty/wpt/checkout.sh

 #!/bin/bash
 #
 # Removes ./wpt/ directory containing the reduced web-platform-tests tree and
 # starts a new checkout. Only files in WPTWhiteList are retained. The revisions
 # getting checked out are defined in WPTHeads.
 
 DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
 cd $DIR
 
 TARGET_DIR=$DIR/wpt
 REMOTE_REPO="https://chromium.googlesource.com/external/w3c/web-platform-tests.git"
 
 function clone {
   # First line is the main repo HEAD.
   WPT_HEAD=$(head -n 1 $DIR/WPTHeads)
 
   # Remove existing repo if already exists.
   [ -d "$TARGET_DIR" ] && rm -rf $TARGET_DIR
 
   # Clone the main repository.
   git clone $REMOTE_REPO $TARGET_DIR
   cd $TARGET_DIR && git checkout $WPT_HEAD
+  echo "WPTHead: " `git rev-parse HEAD`
 
   # Starting from the 2nd line of WPTWhiteList, we read and checkout submodules.
   tail -n+2 $DIR/WPTHeads | while read dir submodule commit; do
     cd $TARGET_DIR/$dir && \
       git submodule update --init $submodule && \
       cd $TARGET_DIR/$dir/$submodule && \
       git checkout $commit
+    echo "WPTHead: $dir $submodule" `git rev-parse HEAD`
   done
 }
 
 function reduce {
+  cd $TARGET_DIR
+  # web-platform-tests/html/ contains a filename with ', and it confuses
+  # xargs on macOS.
+  rm -fr html
   # Remove all except white-listed.
-  cd $TARGET_DIR
   find . -type f | grep -Fxvf ../WPTWhiteList | xargs -n 1 rm
   find . -empty -type d -delete
 }
 
 actions="clone reduce"
 [ "$1" != "" ] && actions="$@"
 
 for action in $actions; do
   type -t $action >/dev/null || (echo "Unknown action: $action" 1>&2 && exit 1)
   $action
 done
 
 # TODO(burnik): Handle the SSL certs and other configuration.