ozone: Implement PlatformObject<T> for platform-specific objects

ui/ozone/platform_selection.cc

+// Copyright 2014 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 "base/command_line.h"
+#include "base/logging.h"
+#include "ui/ozone/ozone_switches.h"
+#include "ui/ozone/platform_list.h"
+
+namespace ui {
+
+namespace {
+
+// Returns the name of the platform to use (value of --ozone-platform flag).
+std::string GetPlatformName() {
+  // The first platform is the default.
+  if (!CommandLine::ForCurrentProcess()->HasSwitch(switches::kOzonePlatform) &&
+      kPlatformCount > 0)
+    return kPlatformNames[0];
+  return CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+      switches::kOzonePlatform);
+}
+
+int g_selected_platform = -1;
+
+}  // namespace
+
+int GetOzonePlatformId() {
+  if (g_selected_platform >= 0)
+    return g_selected_platform;
+
+  std::string platform_name = GetPlatformName();
+
+  // Search for a matching platform in the list.
+  for (int platform_id = 0; platform_id < kPlatformCount; ++platform_id) {
+    if (platform_name == kPlatformNames[platform_id]) {
+      g_selected_platform = platform_id;
+      return g_selected_platform;
+    }
+  }
+
+  LOG(FATAL) << "Invalid ozone platform: " << platform_name;
+  return -1;  // not reached
+}
+
+const char* GetOzonePlatformName() {
+  return kPlatformNames[GetOzonePlatformId()];
+}
+
+}  // namespace ui