Add helpers for creating UI components.

mojo/ui/content_viewer_app.cc

+// Copyright 2015 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 "mojo/ui/content_viewer_app.h"
+
+#include "base/command_line.h"
+#include "base/logging.h"
+
+namespace mojo {
+namespace ui {
+
+class ContentViewerApp::DelegatingContentHandler : public mojo::ContentHandler {
+ public:
+  DelegatingContentHandler(ContentViewerApp* app,
+                           const std::string& content_handler_url)
+      : app_(app), content_handler_url_(content_handler_url) {}
+
+  ~DelegatingContentHandler() override {}
+
+ private:
+  // |ContentHandler|:
+  void StartApplication(
+      mojo::InterfaceRequest<mojo::Application> application_request,
+      mojo::URLResponsePtr response) override {
+    app_->StartViewer(content_handler_url_, application_request.Pass(),
+                      response.Pass());
+  }
+
+  ContentViewerApp* app_;
+  std::string content_handler_url_;
+
+  MOJO_DISALLOW_COPY_AND_ASSIGN(DelegatingContentHandler);
+};
+
+ContentViewerApp::ContentViewerApp() {}
+
+ContentViewerApp::~ContentViewerApp() {}
+
+void ContentViewerApp::Initialize(mojo::ApplicationImpl* app_impl) {
+  app_impl_ = app_impl;
+
+  auto command_line = base::CommandLine::ForCurrentProcess();

[abarth, 2016/01/10 23:23:39]

I'd remove this interaction with the CommandLine static from these helper
classes.  We shouldn't make it easier for folks to fall into this antipattern.

[jeffbrown, 2016/01/26 07:25:15]

I'm going to leave this in for now since it's super useful for examples and
debugging (there's no way at all to set debug log verbosity otherwise). 
Honestly I shouldn't have to write this code at all.  It should be handled by
the ApplicationRunnerChromium as part of setting up the environment but we'll
need to refactor that first.

Created issue #633 to track that problem.

+  command_line->InitFromArgv(app_impl_->args());
+  logging::LoggingSettings settings;
+  settings.logging_dest = logging::LOG_TO_SYSTEM_DEBUG_LOG;
+  logging::InitLogging(settings);
+}
+
+bool ContentViewerApp::ConfigureIncomingConnection(
+    mojo::ApplicationConnection* connection) {
+  connection->AddService<mojo::ContentHandler>(this);
+  return true;
+}
+
+void ContentViewerApp::Create(
+    mojo::ApplicationConnection* connection,
+    mojo::InterfaceRequest<mojo::ContentHandler> request) {
+  bindings_.AddBinding(
+      new DelegatingContentHandler(this, connection->GetConnectionURL()),
+      request.Pass());
+}
+
+void ContentViewerApp::StartViewer(
+    const std::string& content_handler_url,
+    mojo::InterfaceRequest<mojo::Application> application_request,
+    mojo::URLResponsePtr response) {
+  ViewProviderApp* app = LoadContent(content_handler_url, response.Pass());
+  if (app)
+    new mojo::ApplicationImpl(app, application_request.Pass());
+}
+
+}  // namespace ui
+}  // namespace mojo