Refactor language detection logic to allow non-static CLD data sources.

components/translate/content/renderer/renderer_cld_data_provider.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/lazy_instance.h"
+#include "components/translate/content/renderer/renderer_cld_data_provider.h"
+
+namespace {
+translate::RendererCldDataProvider* g_instance;
+
+// The default is a no-op implementation used to avoid a hard-crash if code
+// fails to set a more functional version.
+struct WrappedDefault {
+  WrappedDefault() {
+    value = new translate::RendererCldDataProvider();
+  }
+  translate::RendererCldDataProvider* value;
+};
+base::LazyInstance<WrappedDefault>::Leaky g_wrapped_default =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+
+namespace translate {
+
+RendererCldDataProvider::RendererCldDataProvider() {
+}
+
+bool RendererCldDataProvider::OnMessageReceived(const IPC::Message&) {
+  return true;
+}
+
+void RendererCldDataProvider::SendCldDataRequest() {
+}
+
+bool RendererCldDataProvider::IsCldDataAvailable() {
+  return false;
+}
+
+void RendererCldDataProvider::SetCldAvailableCallback(
+    base::Callback<void(void)> callback) {
+  // No-op
+}
+
+void RendererCldDataProvider::Set(
+    RendererCldDataProvider* instance, bool overwrite) {
+  if (overwrite || g_instance == NULL) {
+    g_instance = instance;
+  }
+}
+
+bool RendererCldDataProvider::IsInitialized() {
+  return g_instance != NULL;
+}
+
+RendererCldDataProvider* RendererCldDataProvider::Get() {
+  if (g_instance == NULL) {
+    // No provider set. OK for test code and narrow use cases, but bad if it is
+    // a real renderer. Since there's no good way to differentiate these use
+    // cases at runtime, don't log a warning here.
+    return g_wrapped_default.Get().value;
+  }
+  return g_instance;
+}
+
+}  // namespace translate