Only call ToString in fuzzer if IsSetConfig.

ToString (which is a test-only method so it doesn't really matter) is
only call if IsSetConfig, not !IsParseError

Bug: 954766
Change-Id: I1e956cb374d5bf9899e16942f6c13868e29e6100
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1577563
Commit-Queue: David Benjamin <davidben@chromium.org>
Auto-Submit: David Benjamin <davidben@chromium.org>
Reviewed-by: Matt Mueller <mattm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#652906}

components/domain_reliability/header.cc

@@ -279,6 +279,7 @@ DomainReliabilityHeader::ReleaseConfig() {
 }
 
 std::string DomainReliabilityHeader::ToString() const {
+  DCHECK_EQ(PARSE_SET_CONFIG, status_);
   std::string string;
   int64_t max_age_s = max_age_.InSeconds();
 

components/domain_reliability/header.h

@@ -44,6 +44,8 @@ class DOMAIN_RELIABILITY_EXPORT DomainReliabilityHeader {
 
   std::unique_ptr<DomainReliabilityConfig> ReleaseConfig();
 
+  // Converts the config to a string. This may only be called if IsSetConfig()
+  // returns true.
   std::string ToString() const;
 
  private:

components/domain_reliability/header_fuzzer.cc

@@ -28,7 +28,7 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
   base::StringPiece input(reinterpret_cast<const char*>(data), size);
   std::unique_ptr<DomainReliabilityHeader> header =
       DomainReliabilityHeader::Parse(input);
-  if (!header->IsParseError()) {
+  if (header->IsSetConfig()) {
     header->ToString();
   }
   return 0;