Wire up process launch error codes.

content/public/browser/utility_process_host_client.h

Index: content/public/browser/utility_process_host_client.h
diff --git a/content/public/browser/utility_process_host_client.h b/content/public/browser/utility_process_host_client.h
index bd7e89d62032e9bda6c2aeb97fe80ebff77d6261..03673d053b78b27483c3d7c5e49970b5ace88709 100644
--- a/content/public/browser/utility_process_host_client.h
+++ b/content/public/browser/utility_process_host_client.h
@@ -23,8 +23,9 @@ class UtilityProcessHostClient
   // Called when the process has crashed.
   virtual void OnProcessCrashed(int exit_code) {}
 
-  // Called when the process fails to launch, i.e. it has no exit code.
-  virtual void OnProcessLaunchFailed() {}
+  // Called when the process fails to launch. |error_code| is the platform
+  // specific error code for why the process failed to launch.

[jam, 2016/04/28 15:41:14]

it's confusing looking at this api what "platform specific" means. in the
context of this cl, it's obvious, but someone looking later won't know.

why not have this be a typedef?

[Will Harris, 2016/05/02 16:45:23]

updated this comment to specify the typedefs used. I can't use the typedef as
there's two different ones so using int.

+  virtual void OnProcessLaunchFailed(int error_code) {}
 
   // Allow the client to filter IPC messages.
   virtual bool OnMessageReceived(const IPC::Message& message) = 0;