Fix race condition when initializing request context getter.

Note that we are calling GetURLRequestContext() in the UI thread when
using the protocol module, this should in fact not be allowed, but for
now we just use the workaround of making sure the request context getter
has been initialized before we use the protocol module.

browser/net/atom_url_request_context_getter.cc

@@ -66,6 +66,7 @@ AtomURLRequestContextGetter::~AtomURLRequestContextGetter() {
 net::URLRequestContext* AtomURLRequestContextGetter::GetURLRequestContext() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
+  base::AutoLock auto_lock(lock_);
   if (!url_request_context_.get()) {
     url_request_context_.reset(new net::URLRequestContext());
     network_delegate_ = network_delegate_factory_.Run().Pass();

browser/net/atom_url_request_context_getter.h

@@ -8,6 +8,7 @@
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/synchronization/lock.h"
 #include "content/public/browser/content_browser_client.h"
 #include "net/url_request/url_request_context_getter.h"
 
@@ -59,6 +60,8 @@ class AtomURLRequestContextGetter : public net::URLRequestContextGetter {
   base::Callback<scoped_ptr<brightray::NetworkDelegate>(void)>
       network_delegate_factory_;
 
+  base::Lock lock_;
+
   scoped_ptr<net::ProxyConfigService> proxy_config_service_;
   scoped_ptr<brightray::NetworkDelegate> network_delegate_;
   scoped_ptr<net::URLRequestContextStorage> storage_;