Add a GN flag to allow sanitizer builds with full debugging symbols.

build/config/sanitizers/sanitizers.gni

 # Copyright 2015 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/toolchain/toolchain.gni")
 
 declare_args() {
   # Compile for Address Sanitizer to find memory bugs.
   is_asan = false
@@ skipping 79 matching lines @@
   # Not for client use.
   disable_libfuzzer = false
 
   # Value for -fsanitize-coverage flag. Setting this causes
   # use_sanitizer_coverage to be enabled.
   # Default value when unset and use_afl=true:
   # trace-pc
   # Default value when unset and use_sanitizer_coverage=true:
   #     edge,indirect-calls,8bit-counters
   sanitizer_coverage_flags = ""
+
+  # Keep symbol level when building with sanitizers. When sanitizers are
+  # enabled, the default is to compile with the minimum debug info level
+  # necessary, overriding any other symbol level arguments that may be set.
+  # Setting this to true prevents this.
+  sanitizer_keep_symbols = false
 }
 
 # Disable sanitizers for non-default toolchains.
 if (current_toolchain != default_toolchain) {
   is_asan = false
   is_cfi = false
   is_lsan = false
   is_msan = false
   is_syzyasan = false
   is_tsan = false
@@ skipping 78 matching lines @@
 assert(!is_debug || !(is_msan || is_ubsan || is_ubsan_null || is_ubsan_vptr),
        "Sanitizers should generally be used in release (set is_debug=false).")
 
 assert(!is_msan || (is_linux && current_cpu == "x64"),
        "MSan currently only works on 64-bit Linux and ChromeOS builds.")
 
 # ASAN build on Windows is not working in debug mode. Intercepting memory
 # allocation functions is hard on Windows and not yet implemented in LLVM.
 assert(!is_win || !is_debug || !is_asan,
        "ASan on Windows doesn't work in debug (set is_debug=false).")