Hang on android when DNS resolution is not done

BUG=webrtc:5139
R=juberti@google.com
TBR=juberti@webrtc.org

Review URL: https://codereview.webrtc.org/1429493009 .

Cr-Commit-Position: refs/heads/master@{#10463}
diff --git a/webrtc/p2p/base/stunport.cc b/webrtc/p2p/base/stunport.cc
index 1598fe4..c0a8975 100644
--- a/webrtc/p2p/base/stunport.cc
+++ b/webrtc/p2p/base/stunport.cc
@@ -116,7 +116,10 @@
 UDPPort::AddressResolver::~AddressResolver() {
   for (ResolverMap::iterator it = resolvers_.begin();
        it != resolvers_.end(); ++it) {
-    it->second->Destroy(true);
+    // TODO(guoweis): Change to asynchronous DNS resolution to prevent the hang
+    // when passing true to the Destroy() which is a safer way to avoid the code
+    // unloaded before the thread exits. Please see webrtc bug 5139.
+    it->second->Destroy(false);
   }
 }