[Variations] Refactor all state used for study filtering into a container struct.

components/variations/client_filterable_state.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 "components/variations/client_filterable_state.h"
+
+#include "build/build_config.h"
+
+namespace variations {
+
+// static
+Study::Platform ClientFilterableState::GetCurrentPlatform() {
+#if defined(OS_WIN)
+  return Study::PLATFORM_WINDOWS;
+#elif defined(OS_IOS)
+  return Study::PLATFORM_IOS;
+#elif defined(OS_MACOSX)
+  return Study::PLATFORM_MAC;
+#elif defined(OS_CHROMEOS)
+  return Study::PLATFORM_CHROMEOS;
+#elif defined(OS_ANDROID)
+  return Study::PLATFORM_ANDROID;
+#elif defined(OS_LINUX) || defined(OS_BSD) || defined(OS_SOLARIS)
+  // Default BSD and SOLARIS to Linux to not break those builds, although these
+  // platforms are not officially supported by Chrome.
+  return Study::PLATFORM_LINUX;
+#else
+#error Unknown platform
+#endif
+}
+
+ClientFilterableState::ClientFilterableState() {}
+ClientFilterableState::~ClientFilterableState() {}
+
+}  // namespace variations