Mus Demo: Add a comment line switch for launching multiple windows in external mode

services/ui/demo/mus_demo_external.cc

 // 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.
 
 #include "services/ui/demo/mus_demo_external.h"
 
+#include "base/command_line.h"
+#include "base/strings/string_number_conversions.h"
 #include "services/service_manager/public/cpp/service_context.h"
 #include "services/ui/demo/window_tree_data.h"
 #include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/window_tree_host.mojom.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/display/display.h"
 
 namespace ui {
 namespace demo {
@@ skipping 12 matching lines @@
     factory->CreateWindowTreeHost(MakeRequest(&host_), std::move(tree_client));
   }
 
  private:
   // Holds the Mojo pointer to the window tree host.
   mojom::WindowTreeHostPtr host_;
 
   DISALLOW_COPY_AND_ASSIGN(WindowTreeDataExternal);
 };
 
-// Number of windows to open.
-// TODO(tonikitoo,fwang): Open multiple windows.
-const size_t kNumberOfWindows = 1;
-
 int GetSquareSizeForWindow(int window_index) {
   return 50 * window_index + 400;
 };
 
 }  // namespace
 
 MusDemoExternal::MusDemoExternal() {}
 
 MusDemoExternal::~MusDemoExternal() {}
 
 std::unique_ptr<aura::WindowTreeClient>
 MusDemoExternal::CreateWindowTreeClient() {
   return base::MakeUnique<aura::WindowTreeClient>(
       context()->connector(), this, nullptr,
       MakeRequest(&window_tree_client_mojo_));
 }
 
 void MusDemoExternal::OnStartImpl() {
+  const base::CommandLine* command_line =
+      base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch("external-window-count")) {
+    if (!base::StringToSizeT(
+            command_line->GetSwitchValueASCII("external-window-count"),
+            &number_of_windows_)) {
+      LOG(ERROR) << "Invalid value for \'external-window-count\'";
+      return;

[kylechar, 2017/03/01 18:39:07]

What happens if we return here without creating anything?

+    }
+  }
+
   // TODO(tonikitoo,fwang): Extend the WindowTreeClient API to allow connection
   // to the window tree host factory using window_tree_client().
   context()->connector()->BindInterface(ui::mojom::kServiceName,
                                         &window_tree_host_factory_);
 
   // TODO(tonikitoo,fwang): Implement management of displays in external mode.
   // For now, a fake display is created in order to work around an assertion in
   // aura::GetDeviceScaleFactorFromDisplay().
   AddPrimaryDisplay(display::Display(0));
 
-  // The number of windows to open is specified by kNumberOfWindows. The windows
-  // are opened sequentially (the first one here and the others after each call
-  // to OnEmbed) to ensure that the WindowTreeHostMus passed to OnEmbed
-  // corresponds to the WindowTreeDataExternal::host_ created in OpenNewWindow.
+  // The number of windows to open is specified by number_of_windows_. The
+  // windows are opened sequentially (the first one here and the others after
+  // each call to OnEmbed) to ensure that the WindowTreeHostMus passed to
+  // OnEmbed corresponds to the WindowTreeDataExternal::host_ created in
+  // OpenNewWindow.
   OpenNewWindow();
 }
 
 void MusDemoExternal::OpenNewWindow() {
   // TODO(tonikitoo,fwang): Extend the WindowTreeClient API to allow creation
   // of window tree host. Then pass window_tree_client() here and remove
   // window_tree_host_factory_ and window_tree_client_mojo_. Currently
   // window_tree_client_mojo_ is only initialized once so this is incorrect when
   // kNumberOfWindows > 1.
   AppendWindowTreeData(base::MakeUnique<WindowTreeDataExternal>(
       window_tree_host_factory_.get(), std::move(window_tree_client_mojo_),
       GetSquareSizeForWindow(initialized_windows_count_)));
 }
 
 void MusDemoExternal::OnEmbed(
     std::unique_ptr<aura::WindowTreeHostMus> window_tree_host) {
   InitWindowTreeData(std::move(window_tree_host));
   initialized_windows_count_++;
 
   // Open the next window until the requested number of windows is reached.
-  if (initialized_windows_count_ < kNumberOfWindows)
+  if (initialized_windows_count_ < number_of_windows_)
     OpenNewWindow();
 }
 
 void MusDemoExternal::OnEmbedRootDestroyed(
     aura::WindowTreeHostMus* window_tree_host) {
   RemoveWindowTreeData(window_tree_host);
 }
 
 }  // namespace demo
 }  // namespace ui