[libfuzzer] separate libfuzzer ubsan configuration and ubsan build config setup.

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 228 matching lines @@
       }
     }
     if (is_ubsan_vptr) {
       ubsan_vptr_blacklist_path =
           rebase_path("//tools/ubsan/vptr_blacklist.txt", root_build_dir)
       cflags += [
         "-fsanitize=vptr",
         "-fsanitize-blacklist=$ubsan_vptr_blacklist_path",
       ]
     }
+    if (is_libfuzzer_ubsan) {

[inferno, 2016/03/25 20:57:55]

please rename this to is_ubsan_security or something like that since we can use
this flag outside of libfuzzer too.

[aizatsky, 2016/03/25 21:02:45]

Done.

+      ubsan_blacklist_path =
+          rebase_path("//tools/ubsan/blacklist.txt", root_build_dir)
+      cflags += [
+        "-fsanitize=signed-integer-overflow",
+        "-fsanitize-blacklist=$ubsan_blacklist_path",
+      ]
+    }
     if (is_lto && !is_nacl) {
       cflags += [ "-flto" ]
 
       if (is_cfi) {
         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 28 matching lines @@
 }
 
 config("default_sanitizer_coverage_flags") {
   cflags = []
 
   if (use_sanitizer_coverage) {
     # FIXME: make this configurable.
     cflags += [ "-fsanitize-coverage=edge,indirect-calls,8bit-counters" ]
   }
 }