Add another TSan suppression for issue 794920.

TBR=glider@chromium.org

Bug: 794920
Change-Id: I46fd3e886acb2db047655c055f0b887971a8c09b
Reviewed-on: https://chromium-review.googlesource.com/1025968Reviewed-by: Abhishek Arya <inferno@chromium.org>
Commit-Queue: Abhishek Arya <inferno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553143}

build/sanitizers/tsan_suppressions.cc

@@ -257,6 +257,7 @@ char kTSanDefaultSuppressions[] =
 
     // https://crbug.com/794920
     "race:base::debug::SetCrashKeyString\n"
+    "race:crash_reporter::internal::CrashKeyStringImpl::Set\n"
 
     // http://crbug.com/795110
     "race:third_party/fontconfig/*\n"