[libfuzzer] use source-built expat parser

third_party/expat/BUILD.gn

Index: third_party/expat/BUILD.gn
diff --git a/third_party/expat/BUILD.gn b/third_party/expat/BUILD.gn
index e70f31be067f4c0562daa86f364b1048e843d29f..c2db9f1aea3d4dc4be81b4890d828c5817b97c3f 100644
--- a/third_party/expat/BUILD.gn
+++ b/third_party/expat/BUILD.gn
@@ -6,7 +6,7 @@ import("//build/config/chromecast_build.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 
 # Chromecast doesn't ship expat as a system library

[Nico, 2016/06/01 15:44:14]

can you add the comment

      # On Linux, we implicitly already depend on expat via fontconfig;
      # let's not pull it in twice.

from the gyp file?

[aizatsky, 2016/06/02 21:02:08]

Done. Also added libfuzzer comment.

-if (is_linux && !is_chromecast) {
+if (is_linux && !is_chromecast && !use_libfuzzer) {
   config("expat_config") {
     libs = [ "expat" ]
   }