Fix DCHECK-only race condition in ProxyResolverV8TracingImpl

Bug: 699562
Change-Id: I9c818a0c0c490b2d32929a9867d5d3bebf6e8ca9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1618016
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Commit-Queue: David Benjamin <davidben@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#661014}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 1e7bfdb26cc8551539d9bf9b94dcc9fd326c55b7

sanitizers/tsan_suppressions.cc

@@ -183,10 +183,6 @@ char kTSanDefaultSuppressions[] =
     // http://crbug.com/633145
     "race:third_party/libjpeg_turbo/simd/jsimd_x86_64.c\n"
 
-    // http://crbug.com/v8/6065
-    "race:net::(anonymous namespace)::ProxyResolverV8TracingImpl::RequestImpl"
-    "::~RequestImpl()\n"
-
     // http://crbug.com/691029
     "deadlock:libGLX.so*\n"