GN: Add support for prebuilt instrumented libraries.

TBR=glider@chromium.org

Review URL: https://codereview.chromium.org/1150193002

Cr-Original-Commit-Position: refs/heads/master@{#332148}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 74f1d187956e64c25724b116ed06ca7d00b89917

config/compiler/BUILD.gn

@@ -57,11 +57,6 @@ declare_args() {
     # The patch is preapplied to the internal toolchain and hence all bots.
     msvs_xtree_patched = false
   }
-
-  # 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 = 2
 }
 
 # default_include_dirs ---------------------------------------------------------
@@ -175,8 +170,6 @@ config("compiler") {
         "-fsanitize-memory-track-origins=$msan_track_origins",
         "-fsanitize-blacklist=$msan_blacklist_path",
       ]
-
-      # TODO(GYP): Support instrumented libraries.
     }
 
     if (use_custom_libcxx) {

config/sanitizers/BUILD.gn

@@ -8,7 +8,9 @@ import("//build/config/sanitizers/sanitizers.gni")
 # shared_libraries. Unconditionally depend upon this target as it is empty if
 # |is_asan|, |is_lsan|, |is_tsan|, |is_msan| and |use_custom_libcxx| are false.
 group("deps") {
-  deps = []
+  deps = [
+    "//third_party/instrumented_libraries:deps",
+  ]
   if (is_asan || is_lsan || is_tsan || is_msan) {
     public_configs = [ ":sanitizer_options_link_helper" ]
     deps += [ ":options_sources" ]

config/sanitizers/sanitizers.gni

@@ -7,4 +7,14 @@ declare_args() {
   # buildtools/third_party/libc++abi) instead of stdlibc++ as standard library.
   # This is intended to be used for instrumented builds.
   use_custom_libcxx = (is_asan && is_linux) || is_tsan || is_msan
+
+  # 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 = 2
+
+  # Use dynamic libraries instrumented by one of the sanitizers instead of the
+  # standard system libraries. Set this flag to download prebuilt binaries from
+  # GCS.
+  use_prebuilt_instrumented_libraries = false
 }