Enable generation of local host candidate.

Source/modules/mediastream/RTCPeerConnection.cpp

Index: Source/modules/mediastream/RTCPeerConnection.cpp
diff --git a/Source/modules/mediastream/RTCPeerConnection.cpp b/Source/modules/mediastream/RTCPeerConnection.cpp
index b3ae4317d8a5817b673b7bd3035222e7243f6680..820b87fc5689929b2aae39f0c94ad14f1766f28c 100644
--- a/Source/modules/mediastream/RTCPeerConnection.cpp
+++ b/Source/modules/mediastream/RTCPeerConnection.cpp
@@ -103,17 +103,28 @@ RTCConfiguration* RTCPeerConnection::parseConfiguration(const Dictionary& config
     }
 
     ArrayValue iceServers;
+    size_t numberOfServers = 0;
+    bool enableLocalhostCandidate = false;
     bool ok = DictionaryHelper::get(configuration, "iceServers", iceServers);
-    if (!ok || iceServers.isUndefinedOrNull()) {
-        exceptionState.throwTypeError("Malformed RTCConfiguration");
-        return 0;
-    }
-
-    size_t numberOfServers;
-    ok = iceServers.length(numberOfServers);
     if (!ok) {
-        exceptionState.throwTypeError("Malformed RTCConfiguration");
-        return 0;
+        v8::Local<v8::Value> iceServersValue;
+        // Failed to parse iceServers as ArrayValue, try it as a scalar.
+        ok = DictionaryHelper::get(configuration, "iceServers", iceServersValue);
+        if (!ok || iceServersValue->IsUndefined()) {
+            // if iceServers is not specified (|ok| is false) or specified as
+            // "undefined", treat it as the special case which generates
+            // localhost candidate.
+            enableLocalhostCandidate = true;
+        } else {
+            exceptionState.throwTypeError("Malformed RTCConfiguration");
+            return 0;
+        }
+    } else {
+        ok = iceServers.length(numberOfServers);
+        if (!ok) {
+            exceptionState.throwTypeError("Malformed RTCConfiguration");
+            return 0;
+        }
     }
 
     RTCBundlePolicy bundlePolicy = RTCBundlePolicyBalanced;
@@ -144,6 +155,7 @@ RTCConfiguration* RTCPeerConnection::parseConfiguration(const Dictionary& config
     rtcConfiguration->setIceTransports(iceTransports);
     rtcConfiguration->setBundlePolicy(bundlePolicy);
     rtcConfiguration->setRtcpMuxPolicy(rtcpMuxPolicy);
+    rtcConfiguration->setEnableLocalhostCandidate(enableLocalhostCandidate);
 
     for (size_t i = 0; i < numberOfServers; ++i) {
         Dictionary iceServer;