Remove unused bailout reasons.

This also adds a script to the tools directory that allows to grep for
unused bailout reasons. For now the script needs to be run manually.

R=mvstanton@chromium.org

Review URL: https://codereview.chromium.org/1237623003

Cr-Commit-Position: refs/heads/master@{#29609}

tools/check-unused-bailouts.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.
+
+v8_root=$(readlink -f $(dirname $BASH_SOURCE)/../)
+bailouts=$(grep -oP 'V\(\K(k[^,]*)' "$v8_root/src/bailout-reason.h")
+
+for bailout in $bailouts; do
+  bailout_uses=$(grep -r $bailout "$v8_root/src" "$v8_root/test/cctest" | wc -l)
+  if [ $bailout_uses -eq "1" ]; then
+    echo "Bailout reason \"$bailout\" seems to be unused."
+  fi
+done
+
+echo "Kthxbye."