Split CrOS-specific TPM, etc., code into a separate file

It's still in //crypto, but now it's a bit more self-contained.

Bug: 125848
Change-Id: I8596aa9f66630625234206986636edcb29853c73
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1857046
Commit-Queue: David Benjamin <davidben@chromium.org>
Reviewed-by: Matt Mueller <mattm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706202}

crypto/BUILD.gn

@@ -116,6 +116,10 @@ component("crypto") {
     ]
   }
 
+  if (is_chromeos) {
+    sources += [ "nss_util_chromeos.cc" ]
+  }
+
   defines = [ "CRYPTO_IMPLEMENTATION" ]
 
   if (is_nacl) {

crypto/nss_util_internal.h

@@ -123,6 +123,14 @@ CRYPTO_EXPORT void SetPrivateSoftwareSlotForChromeOSUserForTesting(
 
 #endif  // defined(OS_CHROMEOS)
 
+// Loads the given module for this NSS session.
+SECMODModule* LoadNSSModule(const char* name,
+                            const char* library_path,
+                            const char* params);
+
+// Returns the current NSS error message.
+std::string GetNSSErrorMessage();
+
 }  // namespace crypto
 
 #endif  // CRYPTO_NSS_UTIL_INTERNAL_H_