Remove -fsanitize=null for ubsan_vptr=1 build.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 378 matching lines @@
       # Track where uninitialized memory originates from. From fastest to
       # slowest: 0 - no tracking, 1 - track only the initial allocation site, 2
       # - track the chain of stores leading from allocation site to use site.
       'msan_track_origins%': 1,
 
       # Enable building with UBSan (Clang's -fsanitize=undefined option).
       # -fsanitize=undefined only works with clang, but ubsan=1 implies clang=1
       # See http://clang.llvm.org/docs/UsersManual.html
       'ubsan%': 0,
 
-      # Enable building with UBsan's vptr (Clang's -fsanitize=vptr -fsanitize=null options).
+      # Enable building with UBsan's vptr (Clang's -fsanitize=vptr option).
       # -fsanitize=vptr only works with clang, but ubsan_vptr=1 implies clang=1
       'ubsan_vptr%': 0,
       'ubsan_vptr_blacklist%': '<(PRODUCT_DIR)/../../tools/ubsan_vptr/blacklist.txt',
 
       # Use the dynamic libraries instrumented by one of the sanitizers
       # instead of the standard system libraries.
       'use_instrumented_libraries%': 0,
 
       # Use libc++ (third_party/libc++ and third_party/libc++abi) instead of
       # stdlibc++ as standard library. This is intended to use for instrumented
@@ skipping 3615 matching lines @@
                   '-Wno-error=unused-function',  # http://crbug.com/162783
                 ],
               }],
             ],
           }],
           ['ubsan_vptr==1', {
             'target_conditions': [
               ['_toolset=="target"', {
                 'cflags': [
                   '-fsanitize=vptr',
-                  '-fsanitize=null',  # Avoid dereferences on null pointer objects.
                   '-fsanitize-blacklist=<(ubsan_vptr_blacklist)',
                 ],
                 'cflags_cc!': [
                   '-fno-rtti',
                 ],
                 'cflags!': [
                   '-fno-rtti',
                 ],
                 'ldflags': [
-                  '-fsanitize=vptr',  # -fsanitize=null is not necessary.
+                  '-fsanitize=vptr',
                 ],
                 'defines': [
                   'UNDEFINED_SANITIZER',
                 ],
               }],
             ],
             'conditions': [
               ['OS=="mac"', {
                 'cflags': [
                   '-Wno-error=unused-function',  # http://crbug.com/162783
@@ skipping 1598 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }