Add LayoutTests for WebCrypto's ECDH algorithm.

LayoutTests/crypto/clone-ecKey-private.html

Index: LayoutTests/crypto/clone-ecKey-private.html
diff --git a/LayoutTests/crypto/clone-ecKey-private.html b/LayoutTests/crypto/clone-ecKey-private.html
index 997130470c96ae4b9e7991292a9f50438753cb6a..bee675e5249f2901a4f7d98d23f8caa419de5082 100644
--- a/LayoutTests/crypto/clone-ecKey-private.html
+++ b/LayoutTests/crypto/clone-ecKey-private.html
@@ -13,14 +13,22 @@ description("Tests structured cloning of EC private keys");
 
 jsTestIsAsync = true;
 
-// Tests the 12 permutations of keys generated by:
+// ECDSA and ECDH support different key usages. Pick either sign or deriveBits depending on the algorithm.
+function signOrDeriveBits(algorithmName) {
+  if (algorithmName == "ECDSA")
+    return ['sign'];
+  if (algorithmName == "ECDH")
+    return ['deriveBits'];
+}
+
+// Tests the 24 permutations of keys generated by:
 //   kPossibleAlgorithms x kPossibleExtractable x kPossibleKeyUsages x kPossibleCurves
 //
 // For practical reasons these tests are not exhaustive.
 
-var kPossibleAlgorithms = ['ECDSA'];
+var kPossibleAlgorithms = ['ECDSA', 'ECDH'];
 var kPossibleExtractable = [true, false];
-var kPossibleKeyUsages = [[], ['sign']];
+var kPossibleKeyUsages = [[], signOrDeriveBits];
 var kPossibleNamedCurves = ['P-256', 'P-384', 'P-521'];
 
 // A mapping from curve name, to PKCS8 data (hex-encoded) for a valid private key.
@@ -38,6 +46,9 @@ function runTest(algorithmName, namedCurve, extractable, keyUsages)
 
     var results = {};
 
+    if (typeof keyUsages == "function")
+      keyUsages = keyUsages(algorithmName);
+
     return crypto.subtle.importKey('pkcs8', importData, importAlgorithm, extractable, keyUsages).then(function(importedKey) {
         results.importedKey = importedKey;
         importedKey.extraProperty = 'hi';