[libfuzzer] Add -fsanitize=shift for is_ubsan_security flag.

build/config/sanitizers/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 # Contains the dependencies needed for sanitizers to link into executables and
 # shared_libraries. Unconditionally depend upon this target as it is empty if
@@ skipping 237 matching lines @@
         rebase_path("//tools/ubsan/vptr_blacklist.txt", root_build_dir)
     cflags += [
       "-fsanitize=vptr",
       "-fsanitize-blacklist=$ubsan_vptr_blacklist_path",
     ]
   }
   if (is_ubsan_security) {
     ubsan_blacklist_path =
         rebase_path("//tools/ubsan/blacklist.txt", root_build_dir)
     cflags += [
-      "-fsanitize=signed-integer-overflow",
+      "-fsanitize=signed-integer-overflow,shift",
       "-fsanitize-blacklist=$ubsan_blacklist_path",
     ]
   }
   if (is_cfi && !is_nacl) {
     cfi_blacklist_path =
         rebase_path("//tools/cfi/blacklist.txt", root_build_dir)
     cflags += [
       "-fsanitize=cfi-vcall",
       "-fsanitize=cfi-derived-cast",
       "-fsanitize=cfi-unrelated-cast",
@@ skipping 37 matching lines @@
     if (target_cpu == "arm") {
       # http://crbug.com/517105
       cflags += [
         "-mllvm",
         "-sanitizer-coverage-block-threshold=0",
       ]
     }
     defines = [ "SANITIZER_COVERAGE" ]
   }
 }