Add new system url request context getter to the blimp engine.

blimp/engine/common/blimp_browser_context.cc

Index: blimp/engine/common/blimp_browser_context.cc
diff --git a/blimp/engine/common/blimp_browser_context.cc b/blimp/engine/common/blimp_browser_context.cc
index d536f7af66e3fcb91b49ab8d9be808e5f8b274f5..823c06f6226a99cc3560509b66f1be7251ea00d4 100644
--- a/blimp/engine/common/blimp_browser_context.cc
+++ b/blimp/engine/common/blimp_browser_context.cc
@@ -97,6 +97,13 @@ BlimpBrowserContext::GetDownloadManagerDelegate() {
   return nullptr;
 }
 
+net::URLRequestContextGetter* BlimpBrowserContext::GetSystemRequestContext() {
+  if (!system_context_getter_) {
+    system_context_getter_ = new BlimpSystemURLRequestContextGetter();
+  }
+  return system_context_getter_.get();
+}
+
 net::URLRequestContextGetter* BlimpBrowserContext::GetRequestContext() {
   return GetDefaultStoragePartition(this)->GetURLRequestContext();
 }