Implement rudimentary touchscreen support in mus.

components/mus/ws/test_utils.cc

 // Copyright 2016 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.
 
 #include "components/mus/ws/test_utils.h"
 
 #include "base/memory/ptr_util.h"
 #include "cc/output/copy_output_request.h"
 #include "components/mus/surfaces/surfaces_state.h"
 #include "components/mus/ws/display_binding.h"
@@ skipping 36 matching lines @@
   void SetCursorById(int32_t cursor) override { *cursor_id_storage_ = cursor; }
   mojom::Rotation GetRotation() override { return mojom::Rotation::VALUE_0; }
   float GetDeviceScaleFactor() override {
     return display_metrics_.device_scale_factor;
   }
   void UpdateTextInputState(const ui::TextInputState& state) override {}
   void SetImeVisibility(bool visible) override {}
   bool IsFramePending() const override { return false; }
   void RequestCopyOfOutput(
       std::unique_ptr<cc::CopyOutputRequest> output_request) override {}
+  int64_t GetDisplayId() const override { return 1; }
 
  private:
   ViewportMetrics display_metrics_;
 
   int32_t* cursor_id_storage_;
 
   DISALLOW_COPY_AND_ASSIGN(TestPlatformDisplay);
 };
 
 ClientWindowId NextUnusedClientWindowId(WindowTree* tree) {
@@ skipping 415 matching lines @@
     return nullptr;
   if (!tree->AddWindow(parent_client_id, client_window_id))
     return nullptr;
   *client_id = client_window_id;
   return tree->GetWindowByClientId(client_window_id);
 }
 
 }  // namespace test
 }  // namespace ws
 }  // namespace mus