[tools] Default to stdin for processing in eval_gc_time.sh

tools/eval_gc_time.sh

 #!/bin/bash
 #
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Convenience Script used to rank GC NVP output.
 
 print_usage_and_die() {
-  echo "Usage: $0 new-gen-rank|old-gen-rank max|avg logfile"
+  echo "Usage: $0 RANK SORT [LOGFILE]"
+  echo ""
+  echo "Arguments:"
+  echo "  RANK: old-gen-rank | new-gen-rank"
+  echo "  SORT: max | avg"
+  echo "  LOGFILE: the file to process. will default to /dev/stdin"
   exit 1
 }
 
-if [ $# -ne 3 ]; then
+if [[ $# -lt 2 || $# -gt 3 ]]; then
   print_usage_and_die
 fi
 
 case $1 in
   new-gen-rank|old-gen-rank)
     OP=$1
     ;;
   *)
     print_usage_and_die
 esac
 
 case $2 in 
   max|avg)
     RANK_MODE=$2
     ;;
   *)
     print_usage_and_die
 esac
 
-LOGFILE=$3
+if [ $# -eq 3 ]; then
+  LOGFILE=$3
+else
+  LOGFILE=/dev/stdin
+fi
 
 GENERAL_INTERESTING_KEYS="\
   pause \
 "
 
 INTERESTING_NEW_GEN_KEYS="\
   ${GENERAL_INTERESTING_KEYS} \
   scavenge \
   weak \
   roots \
@@ skipping 43 matching lines @@
 
 case $OP in
   new-gen-rank)
     cat $LOGFILE | grep "gc=s" \
       | $BASE_DIR/eval_gc_nvp.py \
       --no-histogram \
       --rank $RANK_MODE \
       ${INTERESTING_NEW_GEN_KEYS}
     ;;
   old-gen-rank)
-    cat $LOGFILE | grep "gc=ms" | grep "reduce_memory=0" | grep -v "steps=0" \
+    cat $LOGFILE | grep "gc=ms" \
       | $BASE_DIR/eval_gc_nvp.py \
       --no-histogram \
       --rank $RANK_MODE \
       ${INTERESTING_OLD_GEN_KEYS}
     ;;
   *)
     ;;
 esac