SSLCertificate::GetChain: Return scoped_ptr

Instead of using a raw pointer output parameter. This is a good idea
in general, but will also be very convenient when scoped_ptr is gone,
since unique_ptr doesn't have an .accept() method.

BUG=webrtc:5520

Review URL: https://codereview.webrtc.org/1799233002

Cr-Original-Commit-Position: refs/heads/master@{#12004}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: f5d47860805e37a1e99a478ab7cd33a77ba9007b
diff --git a/base/fakesslidentity.h b/base/fakesslidentity.h
index ec603a5..47ff86d 100644
--- a/base/fakesslidentity.h
+++ b/base/fakesslidentity.h
@@ -68,14 +68,14 @@
                                        digest, size);
     return (*length != 0);
   }
-  virtual bool GetChain(SSLCertChain** chain) const {
+  virtual rtc::scoped_ptr<SSLCertChain> GetChain() const {
     if (certs_.empty())
-      return false;
+      return nullptr;
     std::vector<SSLCertificate*> new_certs(certs_.size());
     std::transform(certs_.begin(), certs_.end(), new_certs.begin(), DupCert);
-    *chain = new SSLCertChain(new_certs);
+    rtc::scoped_ptr<SSLCertChain> chain(new SSLCertChain(new_certs));
     std::for_each(new_certs.begin(), new_certs.end(), DeleteCert);
-    return true;
+    return chain;
   }
 
  private: