DevTools: Fixed crash in tethering

BUG=405472

Review URL: https://codereview.chromium.org/491533002

Cr-Commit-Position: refs/heads/master@{#290811}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@290811 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/devtools/tethering_handler.cc

@@ -110,8 +110,10 @@ class SocketPump : public net::StreamListenSocket::Delegate {
   }
 
   void OnClientWrite(int result) {
-    if (result < 0)
+    if (result < 0) {
       SelfDestruct();
+      return;
+    }
 
     wire_buffer_->set_offset(wire_buffer_->offset() + result);