Benchmark RSA private key parsing.

We do non-trivial work when parsing RSA private keys (RSA_check_key)
and, in some consumers, this is performance-sensitive.

Bug: b/192484677
Change-Id: Ic27f5f11d8bd030de77dd500a826fb2dd7c5b75d
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/49105
Reviewed-by: Adam Langley <agl@google.com>

tool/speed.cc

diff --git a/tool/speed.cc b/tool/speed.cc
index 2d01f4b..613e630 100644
--- a/tool/speed.cc
+++ b/tool/speed.cc
@@ -270,6 +270,16 @@
       return false;
     }
     results.Print(name + " verify (fresh key)");
+
+    if (!TimeFunction(&results, [&]() -> bool {
+          return bssl::UniquePtr<RSA>(RSA_private_key_from_bytes(
+                     kRSAKeys[i].key, kRSAKeys[i].key_len)) != nullptr;
+        })) {
+      fprintf(stderr, "Failed to parse %s key.\n", name.c_str());
+      ERR_print_errors_fp(stderr);
+      return false;
+    }
+    results.Print(name + " private key parse");
   }
 
   return true;