Disable excessive logging in profiling fuzzer.

R=mmoroz@chromium.org
TBR=erikchen@chromium.org

Bug: 900812
Change-Id: I1e7cac38d9d705179aeff95d438a6932febe8cd4
Reviewed-on: https://chromium-review.googlesource.com/c/1317868Reviewed-by: Abhishek Arya <inferno@chromium.org>
Reviewed-by: Max Moroz <mmoroz@chromium.org>
Commit-Queue: Abhishek Arya <inferno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605522}

components/services/heap_profiling/BUILD.gn

@@ -74,6 +74,7 @@ fuzzer_test("profiling_fuzzer") {
   ]
   deps = [
     ":heap_profiling",
+    "//base",
   ]
   libfuzzer_options = [ "max_len = 64000" ]
   dict = "stream_fuzzer.dict"

components/services/heap_profiling/stream_fuzzer.cc

@@ -2,11 +2,20 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "base/logging.h"
 #include "components/services/heap_profiling/receiver.h"
 #include "components/services/heap_profiling/stream_parser.h"
 
 #include <utility>
 
+struct Environment {
+  Environment() {
+    // Disable noisy logging as per "libFuzzer in Chrome" documentation:
+    // testing/libfuzzer/getting_started.md#Disable-noisy-error-message-logging.
+    logging::SetMinLogLevel(logging::LOG_FATAL);
+  }
+};
+
 namespace heap_profiling {
 namespace {
 
@@ -27,6 +36,9 @@ class DummyReceiver : public Receiver {
 
 // Entry point for LibFuzzer.
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
+  // Initialize environment once.
+  static Environment env;
+
   heap_profiling::DummyReceiver receiver;
   scoped_refptr<heap_profiling::StreamParser> parser(
       new heap_profiling::StreamParser(&receiver));