WebCrypto: Add crypto.subtle.verify() to the platform interfaces.

LayoutTests/crypto/resources/common.js

+function importHmacSha1Key()
+{
+    var keyFormat = "spki";
+    var data = new Uint8Array([]);
+    var algorithm = {name: 'hmac', hash: {name: 'sha-1'}};
+    var extractable = false;
+    var keyUsages = ['encrypt', 'decrypt', 'sign', 'verify'];
+
+    return crypto.subtle.importKey(keyFormat, data, algorithm, extractable, keyUsages);
+}
+
+// Builds a hex string representation of any array-like input (array or
+// ArrayBufferView). The output looks like this:
+//    [ab 03 4c 99]
+function byteArrayToHexString(bytes)
+{
+    var hexBytes = [];
+
+    for (var i = 0; i < bytes.length; ++i) {
+        var byteString = bytes[i].toString(16);
+        if (byteString.length < 2)
+            byteString = "0" + byteString;
+        hexBytes.push(byteString);
+    }
+
+    return "[" + hexBytes.join(" ") + "]";
+}
+
+function asciiToArrayBuffer(str)
+{
+    var chars = [];
+    for (var i = 0; i < str.length; ++i)
+        chars.push(str.charCodeAt(i));
+    return new Uint8Array(chars);
+}
+