Introduce net::HttpServerPropertiesManager to manage server-specific properties.

net/url_request/url_request_unittest.cc

Index: net/url_request/url_request_unittest.cc
===================================================================
--- net/url_request/url_request_unittest.cc	(revision 104227)
+++ net/url_request/url_request_unittest.cc	(working copy)
@@ -253,6 +253,9 @@
  public:
   URLRequestTest() : default_context_(new TestURLRequestContext(true)) {
     default_context_->set_network_delegate(&default_network_delegate_);
+    // TODO(rtenneti): We should probably use HttpServerPropertiesManager for
+    // the system URLRequestContext too. There's no reason this should be tied
+    // to a profile.
     default_context_->Init();
   }