Make UsbDeviceHandle::ReleaseInterface asynchronous.

This patch adds a callback to UsbDeviceHandle::ReleaseInterface that is
called when the interface has been released. Previously this result was
returned synchronously while the actual release operation happened in
the background.

In the process I've fixed an issue where libusb_release_interface could
have been called from the UI thread if there were no pending transfers
to delay it.

BUG=None

Review URL: https://codereview.chromium.org/1664023002

Cr-Commit-Position: refs/heads/master@{#373641}

2 files changed, 13 insertions, 5 deletions

diff --git a/extensions/browser/api/usb/usb_api.cc b/extensions/browser/api/usb/usb_api.cc
index 3035239..73099f9 100644
--- a/extensions/browser/api/usb/usb_api.cc
+++ b/extensions/browser/api/usb/usb_api.cc
@@ -925,11 +925,17 @@ ExtensionFunction::ResponseAction UsbReleaseInterfaceFunction::Run() {
     return RespondNow(Error(kErrorNoConnection));
   }
 
-  if (device_handle->ReleaseInterface(parameters->interface_number)) {
-    return RespondNow(NoArguments());
-  } else {
-    return RespondNow(Error(kErrorCannotReleaseInterface));
-  }
+  device_handle->ReleaseInterface(
+      parameters->interface_number,
+      base::Bind(&UsbReleaseInterfaceFunction::OnComplete, this));
+  return RespondLater();
+}
+
+void UsbReleaseInterfaceFunction::OnComplete(bool success) {
+  if (success)
+    Respond(NoArguments());
+  else
+    Respond(Error(kErrorCannotReleaseInterface));
 }
 
 UsbSetInterfaceAlternateSettingFunction::
diff --git a/extensions/browser/api/usb/usb_api.h b/extensions/browser/api/usb/usb_api.h
index 3d1dec1..397b1ad 100644
--- a/extensions/browser/api/usb/usb_api.h
+++ b/extensions/browser/api/usb/usb_api.h
@@ -268,6 +268,8 @@ class UsbReleaseInterfaceFunction : public UsbConnectionFunction {
   // ExtensionFunction:
   ResponseAction Run() override;
 
+  void OnComplete(bool success);
+
   DISALLOW_COPY_AND_ASSIGN(UsbReleaseInterfaceFunction);
 };