Change the WebCrypto behavior when importing EC private keys without a public key.

content/test/data/webcrypto/ec_private_keys.json

Index: content/test/data/webcrypto/ec_private_keys.json
diff --git a/content/test/data/webcrypto/ec_private_keys.json b/content/test/data/webcrypto/ec_private_keys.json
index 4d695b498285affcf479c0e19d3f75bcaea8ab8b..bf75a06f822972d7b7c0c46073c74ab4fd2a19ce 100644
--- a/content/test/data/webcrypto/ec_private_keys.json
+++ b/content/test/data/webcrypto/ec_private_keys.json
@@ -73,5 +73,24 @@
       "y":"gKEET8d0MXwkffogoA-3jRQZjTSmNxeUfoxxQ-y53xM"
     },
     "pkcs8": "308186020100301306072A8648CE3D020106082A8648CE3D030107046C306A020101041FC766C09343D4337EEAD05A5CE16C899808C8F15C7C7A4C7DF7231C84C2D5BCA14403420004B7D3CC5D085D8B7707B3E572D223F16CD5E277D3FB93FB1B1B11B2728463CEC580A1044FC774317C247DFA20A00FB78D14198D34A63717947E8C7143ECB9DF13"
+  },
+
+  // In this test the PKCS8 input data does NOT contain the optional publicKey field.
+  //  * When importing from PKCS8 and then exporting to JWK, the "x" and "y"
+  //    parameters are synthesized.
+  //  * When importing from PKCS8 and then exporting back to PKCS8, the
+  //    publicKey field is added. The input is "pkcs8_input", and the expected
+  //    exported data is "pkcs8"
+  {
+    "curve": "P-256",
+    "jwk": {
+      "kty": "EC",
+      "crv": "P-256",
+      "d": "H-M5UMX0YRJK6ZLCvf3xxzsWFfVxvVZ-YNGaofSM30I",
+      "x": "fBEMZtz9qAf25p5F3bPHT2mhSE0gPo3Frajpqd18s8c",
+      "y": "DfRImG5RveXRV2-ZkB-cLGqAakf9kHZDpyuDVZfvyMY"
+    },
+    "pkcs8_input": "3041020100301306072A8648CE3D020106082A8648CE3D0301070427302502010104201FE33950C5F461124AE992C2BDFDF1C73B1615F571BD567E60D19AA1F48CDF42",
+    "pkcs8": "308187020100301306072A8648CE3D020106082A8648CE3D030107046D306B02010104201FE33950C5F461124AE992C2BDFDF1C73B1615F571BD567E60D19AA1F48CDF42A144034200047C110C66DCFDA807F6E69E45DDB3C74F69A1484D203E8DC5ADA8E9A9DD7CB3C70DF448986E51BDE5D1576F99901F9C2C6A806A47FD907643A72B835597EFC8C6"
   }
 ]