Add fuzzer to test Fuzz URLRequestDataJob

net/base/fuzzed_data_provider.h

Index: net/base/fuzzed_data_provider.h
diff --git a/net/base/fuzzed_data_provider.h b/net/base/fuzzed_data_provider.h
index bd8ddbebb21a6c773e45cf76259ffcc931b07704..47a45061cdf248b9a2da0bd5e94fb1399f04ba6b 100644
--- a/net/base/fuzzed_data_provider.h
+++ b/net/base/fuzzed_data_provider.h
@@ -51,6 +51,9 @@ class FuzzedDataProvider {
   // ConsumeValueInRange(0, 0xFFFF).
   uint16_t ConsumeUint16();
 
+  // Reports the remaining bytes available for fuzzed input.
+  size_t remaining_bytes() { return remaining_data_.length(); }
+
  private:
   base::StringPiece remaining_data_;