sanitizers: set is_lsan=true if use_libfuzzer and is_asan are set (linux)

build/config/sanitizers/sanitizers.gni

Index: build/config/sanitizers/sanitizers.gni
diff --git a/build/config/sanitizers/sanitizers.gni b/build/config/sanitizers/sanitizers.gni
index 881ea32bf606d6dea1bc9a5d1c7101c8a10c018f..f28d31600da62ebc0d988e5a13a9a4fb4d995306 100644
--- a/build/config/sanitizers/sanitizers.gni
+++ b/build/config/sanitizers/sanitizers.gni
@@ -155,6 +155,10 @@ assert(!using_sanitizer || is_clang,
 prebuilt_instrumented_libraries_available =
     is_msan && (msan_track_origins == 0 || msan_track_origins == 2)
 
+if (use_libfuzzer && is_asan) {

[inferno, 2016/10/17 17:03:19]

Add is_linux. since in next few months, libfuzzer will be enabled on windows.
and also, this will fail on mac.

Also add a comment to tell why we do this.

[Oliver Chang, 2016/10/17 17:07:21]

Done.

+  is_lsan = true
+}
+
 # MSan only links Chrome properly in release builds (brettw -- 9/1/2015). The
 # same is possibly true for the other non-ASan sanitizers. But regardless of
 # whether it links, one would normally never run a sanitizer in debug mode.