Linux UI: Dynamically respond to changes in the scale factor

ui/views/linux_ui/device_scale_factor_observer.h

Index: ui/views/linux_ui/device_scale_factor_observer.h
diff --git a/ui/views/linux_ui/device_scale_factor_observer.h b/ui/views/linux_ui/device_scale_factor_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..c62bfeb293bbd406bfdd4f8e3a038b5b662cd218
--- /dev/null
+++ b/ui/views/linux_ui/device_scale_factor_observer.h
@@ -0,0 +1,19 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_VIEWS_LINUX_UI_DEVICE_SCALE_FACTOR_OBSERVER_H_
+#define UI_VIEWS_LINUX_UI_DEVICE_SCALE_FACTOR_OBSERVER_H_
+
+namespace views {
+
+class DeviceScaleFactorObserver {
+ public:
+  virtual ~DeviceScaleFactorObserver() {}
+
+  virtual void OnDeviceScaleFactorChanged() = 0;
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_LINUX_UI_DEVICE_SCALE_FACTOR_OBSERVER_H_