Convert //shell/... to use set_connection_error_handler() instead of set_error_handler().

(The latter is deprecated.)

R=rudominer@chromium.org

Review URL: https://codereview.chromium.org/1219683015 .
diff --git a/shell/child_process_host.h b/shell/child_process_host.h
index 67f243d..d065ce6 100644
--- a/shell/child_process_host.h
+++ b/shell/child_process_host.h
@@ -27,10 +27,12 @@
 //
 // This class is not thread-safe. It should be created/used/destroyed on a
 // single thread.
-class ChildProcessHost : public mojo::ErrorHandler {
+class ChildProcessHost {
  public:
   explicit ChildProcessHost(Context* context);
-  ~ChildProcessHost() override;
+  // TODO(vtl): Virtual because |DidStart()| is, even though it shouldn't be
+  // (see |DidStart()|).
+  virtual ~ChildProcessHost();
 
   // |Start()|s the child process; calls |DidStart()| (on the thread on which
   // |Start()| was called) when the child has been started (or failed to start).
@@ -73,9 +75,7 @@
   base::Process DoLaunch(scoped_ptr<LaunchData> launch_data);
 
   void AppCompleted(int32_t result);
-
-  // |mojo::ErrorHandler| methods:
-  void OnConnectionError() override;
+  void OnConnectionError();
 
   Context* const context_;