GN: Implement is_lsan, is_tsan and is_msan.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 26bcd7d9fffff7fa6752cc3054ff9206010e4d85..eea52524483be4eed4d72356212f767c9d6f6c41 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -136,13 +136,31 @@ config("feature_flags") {
   if (use_allocator != "tcmalloc") {
     defines += [ "NO_TCMALLOC" ]
   }
-  if (is_asan) {
+  if (is_asan || is_lsan || is_tsan || is_msan) {
     defines += [
-      "ADDRESS_SANITIZER",
       "MEMORY_TOOL_REPLACES_ALLOCATOR",
       "MEMORY_SANITIZER_INITIAL_SIZE",
     ]
   }
+  if (is_asan) {
+    defines += [ "ADDRESS_SANITIZER" ]
+  }
+  if (is_lsan) {
+    defines += [
+      "LEAK_SANITIZER",
+      "WTF_USE_LEAK_SANITIZER=1",
+    ]
+  }
+  if (is_tsan) {
+    defines += [
+      "THREAD_SANITIZER",
+      "DYNAMIC_ANNOTATIONS_EXTERNAL_IMPL=1",
+      "WTF_USE_DYNAMIC_ANNOTATIONS_NOIMPL=1",
+    ]
+  }
+  if (is_msan) {
+    defines += [ "MEMORY_SANITIZER" ]
+  }
   if (enable_webrtc) {
     defines += [ "ENABLE_WEBRTC=1" ]
   }
@@ -287,7 +305,12 @@ config("release") {
   # Sanitizers.
   # TODO(GYP) The GYP build has "release_valgrind_build == 0" for this
   # condition. When Valgrind is set up, we need to do the same here.
-  if (!is_tsan) {
+  if (is_tsan) {
+    defines += [
+      "DYNAMIC_ANNOTATIONS_ENABLED=1",
+      "WTF_USE_DYNAMIC_ANNOTATIONS=1",
+    ]
+  } else {
     defines += [ "NVALGRIND" ]
     if (!is_nacl) {
       # NaCl always enables dynamic annotations. Currently this value is set to