Rewrite scoped_ptr<T>(NULL) to use the default ctor.

apps/app_shim/app_shim_host_mac.cc

Index: apps/app_shim/app_shim_host_mac.cc
diff --git a/apps/app_shim/app_shim_host_mac.cc b/apps/app_shim/app_shim_host_mac.cc
index 3b4423b3bca4e3c8160b3f099adddc0580cceeb3..097cb2f7cb7c3f2eec07d89b5c095025375a06f3 100644
--- a/apps/app_shim/app_shim_host_mac.cc
+++ b/apps/app_shim/app_shim_host_mac.cc
@@ -14,9 +14,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "ipc/ipc_channel_proxy.h"
 
-AppShimHost::AppShimHost()
-    : channel_(NULL), profile_(NULL) {
-}
+AppShimHost::AppShimHost() : profile_(NULL) {}
 
 AppShimHost::~AppShimHost() {
   DCHECK(CalledOnValidThread());