Add fuzzer for PRTime() from NSPR.

testing/libfuzzer/fuzzers/BUILD.gn

Index: testing/libfuzzer/fuzzers/BUILD.gn
diff --git a/testing/libfuzzer/fuzzers/BUILD.gn b/testing/libfuzzer/fuzzers/BUILD.gn
index 658f206d75a088fa06b2e613e58ef8943191fdc4..c1ab1f6c273f20257cae53b06b95eee2eb60d48e 100644
--- a/testing/libfuzzer/fuzzers/BUILD.gn
+++ b/testing/libfuzzer/fuzzers/BUILD.gn
@@ -336,3 +336,14 @@ fuzzer_test("skia_pathop_fuzzer") {
   ]
   libfuzzer_options = [ "max_len=512" ]
 }
+
+fuzzer_test("prtime_fuzzer") {
+  sources = [
+    "//base/third_party/nspr/fuzz/prtime_fuzzer.cc",

[danakj, 2016/09/15 23:51:01]

It looks like the sources for every other target are in this current directory,
why is this one different?

+  ]
+  deps = [
+    "//base",
+  ]
+  dict = "//base/third_party/nspr/fuzz/prtime.dict"
+  libfuzzer_options = [ "max_len=1024" ]
+}