Fix missing callback chaining in UsbService.

On OS_CHROMEOS when the permission_broker checks a set of devices the
UsbService needs to wait for the async work to complete before responding.
This worked on OS_CHROMEOS desktop builds because the stub implementation of
PermissionBrokerClient wasn't racing to modify the devices vector.

BUG=chromium-os:38836

Review URL: https://chromiumcodereview.appspot.com/12226137

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182320 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 16 insertions, 6 deletions

diff --git a/chrome/browser/usb/usb_service.cc b/chrome/browser/usb/usb_service.cc
index 21e2e33..fcad23d 100644
--- a/chrome/browser/usb/usb_service.cc
+++ b/chrome/browser/usb/usb_service.cc
@@ -70,30 +70,38 @@ void UsbService::Cleanup() {
 
 void UsbService::FindDevices(const uint16 vendor_id,
                              const uint16 product_id,
-                             vector<scoped_refptr<UsbDevice> >* devices) {
+                             vector<scoped_refptr<UsbDevice> >* devices,
+                             const base::Callback<void()>& callback) {
   DCHECK(event_handler_) << "FindDevices called after event handler stopped.";
 #if defined(OS_CHROMEOS)
   chromeos::PermissionBrokerClient* client =
       chromeos::DBusThreadManager::Get()->GetPermissionBrokerClient();
   DCHECK(client) << "Could not get permission broker client.";
-  if (!client)
+  if (!client) {
+    callback.Run();
     return;
+  }
+
   client->RequestUsbAccess(vendor_id,
                            product_id,
                            base::Bind(&UsbService::FindDevicesImpl,
                                       base::Unretained(this),
                                       vendor_id,
                                       product_id,
-                                      devices));
+                                      devices,
+                                      callback));
 #else
-  FindDevicesImpl(vendor_id, product_id, devices, true);
+  FindDevicesImpl(vendor_id, product_id, devices, callback, true);
 #endif  // defined(OS_CHROMEOS)
 }
 
 void UsbService::FindDevicesImpl(const uint16 vendor_id,
                                  const uint16 product_id,
                                  vector<scoped_refptr<UsbDevice> >* devices,
+                                 const base::Callback<void()>& callback,
                                  bool success) {
+  base::ScopedClosureRunner run_callback(callback);
+
   devices->clear();
 
   // If the permission broker was unable to obtain permission for the specified
diff --git a/chrome/browser/usb/usb_service.h b/chrome/browser/usb/usb_service.h
index b18c71d..3987786d3 100644
--- a/chrome/browser/usb/usb_service.h
+++ b/chrome/browser/usb/usb_service.h
@@ -33,10 +33,11 @@ class UsbService : public ProfileKeyedService {
 
   // Find all of the devices attached to the system that are identified by
   // |vendor_id| and |product_id|, inserting them into |devices|. Clears
-  // |devices| before use.
+  // |devices| before use. Calls |callback| once |devices| is populated.
   void FindDevices(const uint16 vendor_id,
                    const uint16 product_id,
-                   std::vector<scoped_refptr<UsbDevice> >* devices);
+                   std::vector<scoped_refptr<UsbDevice> >* devices,
+                   const base::Callback<void()>& callback);
 
   // This function should not be called by normal code. It is invoked by a
   // UsbDevice's Close function and disposes of the associated platform handle.
@@ -73,6 +74,7 @@ class UsbService : public ProfileKeyedService {
   void FindDevicesImpl(const uint16 vendor_id,
                        const uint16 product_id,
                        std::vector<scoped_refptr<UsbDevice> >* devices,
+                       const base::Callback<void()>& callback,
                        bool success);
 
   // Populates |output| with the result of enumerating all attached USB devices.