Make asan blacklists optional

Default is still on but the use of blacklists for asan can be
disabled by setting asan_use_blacklist to false.

This is useful for distributed compilers such as icecc where
flags as -fsanitize-blacklist= pointing to a local source file
is not yet supported.

Bug: 818190
Change-Id: I828ada1142ef76ecc0f1ccad8bd41390f0cbceea
Reviewed-on: https://chromium-review.googlesource.com/c/946101
Commit-Queue: Joel Klinghed <the_jk@opera.com>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#629534}

build/config/sanitizers/BUILD.gn

@@ -300,19 +300,22 @@ config("asan_flags") {
         "-asan-globals=0",
       ]
     }
-    if (is_win) {
-      if (!defined(asan_win_blacklist_path)) {
-        asan_win_blacklist_path =
-            rebase_path("//tools/memory/asan/blacklist_win.txt", root_build_dir)
-      }
-      cflags += [ "-fsanitize-blacklist=$asan_win_blacklist_path" ]
-    } else {
-      # TODO(rnk): Remove this as discussed in http://crbug.com/427202.
-      if (!defined(asan_blacklist_path)) {
-        asan_blacklist_path =
-            rebase_path("//tools/memory/asan/blacklist.txt", root_build_dir)
+    if (asan_use_blacklist) {
+      if (is_win) {
+        if (!defined(asan_win_blacklist_path)) {
+          asan_win_blacklist_path =
+              rebase_path("//tools/memory/asan/blacklist_win.txt",
+                          root_build_dir)
+        }
+        cflags += [ "-fsanitize-blacklist=$asan_win_blacklist_path" ]
+      } else {
+        # TODO(rnk): Remove this as discussed in http://crbug.com/427202.
+        if (!defined(asan_blacklist_path)) {
+          asan_blacklist_path =
+              rebase_path("//tools/memory/asan/blacklist.txt", root_build_dir)
+        }
+        cflags += [ "-fsanitize-blacklist=$asan_blacklist_path" ]
       }
-      cflags += [ "-fsanitize-blacklist=$asan_blacklist_path" ]
     }
   }
 }

build/config/sanitizers/sanitizers.gni

@@ -109,6 +109,9 @@ declare_args() {
   # Default value when unset and use_sanitizer_coverage=true:
   #     trace-pc-guard,indirect-calls
   sanitizer_coverage_flags = ""
+
+  # Use blacklists from tools/memory/asan when compiling with asan.
+  asan_use_blacklist = true
 }
 
 # Disable sanitizers for non-default toolchains.