Improve unit testing of socket API (reland).

chrome/browser/extensions/api/socket/socket_api.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/api/socket/socket_api.h"
 
 #include "base/bind.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/api/dns/host_resolver_wrapper.h"
 #include "chrome/browser/extensions/api/socket/socket.h"
@@ skipping 24 matching lines @@
 
 SocketAsyncApiFunction::SocketAsyncApiFunction()
     : manager_(NULL) {
 }
 
 SocketAsyncApiFunction::~SocketAsyncApiFunction() {
 }
 
 bool SocketAsyncApiFunction::PrePrepare() {
   manager_ = ExtensionSystem::Get(profile())->socket_manager();
+  DCHECK(manager_) << "There is no socket manager. "
+    "If this assertion is failing during a test, then it is likely that "
+    "TestExtensionSystem is failing to provide an instance of "
+    "ApiResourceManager<Socket>.";
   return manager_ != NULL;
 }
 
 bool SocketAsyncApiFunction::Respond() {
   return error_.empty();
 }
 
 SocketExtensionWithDnsLookupFunction::SocketExtensionWithDnsLookupFunction()
     : io_thread_(g_browser_process->io_thread()),
       request_handle_(new net::HostResolver::RequestHandle),
@@ skipping 388 matching lines @@
   bool result = false;
   Socket* socket = manager_->Get(params_->socket_id);
   if (socket)
     result = socket->SetNoDelay(params_->no_delay);
   else
     error_ = kSocketNotFoundError;
   SetResult(Value::CreateBooleanValue(result));
 }
 
 }  // namespace extensions