Add path open errors from the permission broker to the device log.

This change adds an additional ErrorCallback parameter to the permission
broker client so that the caller can get a better log message when its
request to open a device node fails.

This will hopefully help to determine the cause of the many "Did not get
valid device handle from permission broker" errors that some users are
seeing.

BUG=570784

Review URL: https://codereview.chromium.org/1681383002

Cr-Commit-Position: refs/heads/master@{#374571}

1 files changed, 10 insertions, 2 deletions

diff --git a/chromeos/dbus/permission_broker_client.h b/chromeos/dbus/permission_broker_client.h
index 276bfba..f56bfcc 100644
--- a/chromeos/dbus/permission_broker_client.h
+++ b/chromeos/dbus/permission_broker_client.h
@@ -34,6 +34,12 @@ class CHROMEOS_EXPORT PermissionBrokerClient : public DBusClient {
   // An OpenPathCallback callback is run when an OpenPath request is completed.
   typedef base::Callback<void(dbus::FileDescriptor)> OpenPathCallback;
 
+  // An ErrorCallback callback is run when an error is returned by the
+  // permission broker.
+  typedef base::Callback<void(const std::string& error_name,
+                              const std::string& message)>
+      ErrorCallback;
+
   ~PermissionBrokerClient() override;
 
   static PermissionBrokerClient* Create();
@@ -46,9 +52,11 @@ class CHROMEOS_EXPORT PermissionBrokerClient : public DBusClient {
                                const ResultCallback& callback) = 0;
 
   // OpenPath requests that the permission broker open the device node
-  // identified by |path| and return the resulting file descriptor.
+  // identified by |path| and return the resulting file descriptor. One of
+  // |callback| or |error_callback| is called.
   virtual void OpenPath(const std::string& path,
-                        const OpenPathCallback& callback) = 0;
+                        const OpenPathCallback& callback,
+                        const ErrorCallback& error_callback) = 0;
 
   // Requests the |port| be opened on the firewall for incoming TCP/IP
   // connections received on |interface| (an empty string indicates all