[webcrypto] Add deriveBits key_op to JWK import/export.

content/child/webcrypto/jwk.cc

Index: content/child/webcrypto/jwk.cc
diff --git a/content/child/webcrypto/jwk.cc b/content/child/webcrypto/jwk.cc
index 6802819f25d1f3696f03d9487c502274fa876cbc..860418fabd6177de8ccbff6840250f18e96c89b9 100644
--- a/content/child/webcrypto/jwk.cc
+++ b/content/child/webcrypto/jwk.cc
@@ -71,7 +71,7 @@
 //   | "wrapKey"    | key wrap                                              |
 //   | "unwrapKey"  | key unwrap                                            |
 //   | "deriveKey"  | key derivation                                        |
-//   | "deriveBits" | key derivation TODO(padolph): not currently supported |
+//   | "deriveBits" | key derivation                                        |
 //   +-------+--------------------------------------------------------------+
 //
 // - use (Key Use)
@@ -199,11 +199,10 @@ blink::WebCryptoAlgorithm CreateRsaOaepImportAlgorithm(
 }
 
 // Web Crypto equivalent usage mask for JWK 'use' = 'enc'.
-// TODO(padolph): Add 'deriveBits' once supported by Blink.
 const blink::WebCryptoKeyUsageMask kJwkEncUsage =
     blink::WebCryptoKeyUsageEncrypt | blink::WebCryptoKeyUsageDecrypt |
     blink::WebCryptoKeyUsageWrapKey | blink::WebCryptoKeyUsageUnwrapKey |
-    blink::WebCryptoKeyUsageDeriveKey;
+    blink::WebCryptoKeyUsageDeriveKey | blink::WebCryptoKeyUsageDeriveBits;
 // Web Crypto equivalent usage mask for JWK 'use' = 'sig'.
 const blink::WebCryptoKeyUsageMask kJwkSigUsage =
     blink::WebCryptoKeyUsageSign | blink::WebCryptoKeyUsageVerify;