[Blimp] Adds blimp engine browser test framework and LoadUrl test.

blimp/engine/session/blimp_engine_session.cc

Index: blimp/engine/session/blimp_engine_session.cc
diff --git a/blimp/engine/session/blimp_engine_session.cc b/blimp/engine/session/blimp_engine_session.cc
index 3bf21099009ceb698e7e80c39e1545b96c552d6e..687171200ca5784fc0a45f2252dd50b5f1c81ea8 100644
--- a/blimp/engine/session/blimp_engine_session.cc
+++ b/blimp/engine/session/blimp_engine_session.cc
@@ -102,9 +102,8 @@ uint16_t GetListeningPort() {
           &port_parsed)) {
     return kDefaultPort;
   }
-  if (port_parsed == 0 ||
-      port_parsed > 65535) {
-    LOG(FATAL) << "--engine-port must be a value between 1 and 65535.";
+  if (port_parsed > 65535) {
+    LOG(FATAL) << "--engine-port must be a value between 0 and 65535.";
     return kDefaultPort;
   }
   return port_parsed;
@@ -129,6 +128,8 @@ class EngineNetworkComponents : public ConnectionHandler,
   // received messages can be properly handled.
   void Initialize(const std::string& client_token);
 
+  uint16_t GetPortForTesting() { return port_; }
+
   BrowserConnectionHandler* GetBrowserConnectionHandler();
 
  private:
@@ -142,6 +143,7 @@ class EngineNetworkComponents : public ConnectionHandler,
 
   net::NetLog* net_log_;
   base::Closure quit_closure_;
+  uint16_t port_ = 0;
 
   std::unique_ptr<BrowserConnectionHandler> connection_handler_;
   std::unique_ptr<EngineAuthenticationHandler> authentication_handler_;
@@ -176,8 +178,11 @@ void EngineNetworkComponents::Initialize(const std::string& client_token) {
 
   // Adds BlimpTransports to connection_manager_.
   net::IPEndPoint address(GetIPv4AnyAddress(), GetListeningPort());
-  connection_manager_->AddTransport(
-      base::WrapUnique(new TCPEngineTransport(address, net_log_)));
+  TCPEngineTransport* transport = new TCPEngineTransport(address, net_log_);
+  connection_manager_->AddTransport(base::WrapUnique(transport));
+
+  transport->GetLocalAddress(&address);
+  port_ = address.port();
 }
 
 void EngineNetworkComponents::HandleConnection(
@@ -269,6 +274,15 @@ void BlimpEngineSession::Initialize() {
                  engine_config_->client_token()));
 }
 
+void BlimpEngineSession::GetEnginePortForTesting(
+    const GetPortCallback& callback) {
+  content::BrowserThread::PostTaskAndReplyWithResult(
+      content::BrowserThread::IO, FROM_HERE,
+      base::Bind(&EngineNetworkComponents::GetPortForTesting,
+                 base::Unretained(net_components_.get())),
+      callback);
+}
+
 void BlimpEngineSession::RegisterFeatures() {
   thread_pipe_manager_.reset(new ThreadPipeManager(
       content::BrowserThread::GetMessageLoopProxyForThread(