Implement tab indicator for WebUSB.

device/usb/mojo/device_impl.cc

Index: device/usb/mojo/device_impl.cc
diff --git a/device/usb/mojo/device_impl.cc b/device/usb/mojo/device_impl.cc
index 2dee0338f8885e1d2012cb10caeb020f550bee34..43fe8d8264786f629e1c0a0894bbda9e2303a976 100644
--- a/device/usb/mojo/device_impl.cc
+++ b/device/usb/mojo/device_impl.cc
@@ -146,8 +146,11 @@ DeviceImpl::~DeviceImpl() {
 }
 
 void DeviceImpl::CloseHandle() {
-  if (device_handle_)
+  if (device_handle_) {
     device_handle_->Close();
+    if (permission_provider_)
+      permission_provider_->DecrementConnectionCount();
+  }
   device_handle_ = nullptr;
 }
 
@@ -194,6 +197,8 @@ bool DeviceImpl::HasControlTransferPermission(
 void DeviceImpl::OnOpen(const OpenCallback& callback,
                         scoped_refptr<UsbDeviceHandle> handle) {
   device_handle_ = handle;
+  if (device_handle_ && permission_provider_)
+    permission_provider_->IncrementConnectionCount();
   callback.Run(handle ? OpenDeviceError::OK : OpenDeviceError::ACCESS_DENIED);
 }