Reland r288013: First cut at "content handling" support in Mojo.

TBR=darin@chromium.org

Review URL: https://codereview.chromium.org/456533002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288383 0039d316-1c4b-4281-b951-d872f2087c98

33 files changed, 705 insertions, 246 deletions

diff --git a/mojo/examples/content_handler_demo/content_handler_demo.cc b/mojo/examples/content_handler_demo/content_handler_demo.cc
new file mode 100644
index 0000000..21864f7
--- /dev/null
+++ b/mojo/examples/content_handler_demo/content_handler_demo.cc
@@ -0,0 +1,89 @@
+// 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 <stdio.h>
+
+#include "mojo/public/cpp/application/application_delegate.h"
+#include "mojo/public/cpp/application/application_impl.h"
+#include "mojo/public/cpp/application/interface_factory_impl.h"
+#include "mojo/services/public/interfaces/content_handler/content_handler.mojom.h"
+
+namespace mojo {
+namespace examples {
+
+class ContentHandlerApp;
+
+class ContentHandlerImpl : public InterfaceImpl<ContentHandler> {
+ public:
+  explicit ContentHandlerImpl(ContentHandlerApp* content_handler_app)
+      : content_handler_app_(content_handler_app) {
+  }
+  virtual ~ContentHandlerImpl() {}
+
+ private:
+  virtual void OnConnect(const mojo::String& url,
+                         URLResponsePtr content,
+                         ServiceProviderPtr service_provider) MOJO_OVERRIDE;
+
+  ContentHandlerApp* content_handler_app_;
+};
+
+class ContentHandlerApp : public ApplicationDelegate {
+ public:
+  ContentHandlerApp() : content_handler_factory_(this) {
+  }
+
+  virtual void Initialize(ApplicationImpl* app) MOJO_OVERRIDE {
+  }
+
+  virtual bool ConfigureIncomingConnection(ApplicationConnection* connection)
+      MOJO_OVERRIDE {
+    connection->AddService(&content_handler_factory_);
+    return true;
+  }
+
+  void PrintResponse(ScopedDataPipeConsumerHandle body) const {
+    for (;;) {
+      char buf[512];
+      uint32_t num_bytes = sizeof(buf);
+      MojoResult result = ReadDataRaw(body.get(), buf, &num_bytes,
+                                      MOJO_READ_DATA_FLAG_NONE);
+      if (result == MOJO_RESULT_SHOULD_WAIT) {
+        Wait(body.get(),
+             MOJO_HANDLE_SIGNAL_READABLE,
+             MOJO_DEADLINE_INDEFINITE);
+      } else if (result == MOJO_RESULT_OK) {
+        if (fwrite(buf, num_bytes, 1, stdout) != 1) {
+          printf("\nUnexpected error writing to file\n");
+          break;
+        }
+      } else {
+        break;
+      }
+
+      printf("\n>>> EOF <<<\n");
+    }
+  }
+
+ private:
+  InterfaceFactoryImplWithContext<ContentHandlerImpl,
+                                  ContentHandlerApp> content_handler_factory_;
+};
+
+void ContentHandlerImpl::OnConnect(const mojo::String& url,
+                                   URLResponsePtr content,
+                                   ServiceProviderPtr service_provider) {
+  printf("ContentHandler::OnConnect - url:%s - body follows\n\n",
+         url.To<std::string>().c_str());
+  content_handler_app_->PrintResponse(content->body.Pass());
+}
+
+}  // namespace examples
+
+// static
+ApplicationDelegate* ApplicationDelegate::Create() {
+  return new examples::ContentHandlerApp();
+}
+
+}  // namespace mojo
diff --git a/mojo/mojo.gyp b/mojo/mojo.gyp
index ecea8dee..810edd2 100644
--- a/mojo/mojo.gyp
+++ b/mojo/mojo.gyp
@@ -27,6 +27,7 @@
         'mojo_base.gyp:mojo_base',
         'mojo_apps_js_unittests',
         'mojo_compositor_app',
+        'mojo_content_handler_demo',
         'mojo_echo_client',
         'mojo_echo_service',
         'mojo_example_apptests',
@@ -341,6 +342,8 @@
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../net/net.gyp:net',
         '../url/url.gyp:url_lib',
+        'mojo_content_handler_bindings',
+        'mojo_network_bindings',
         'mojo_base.gyp:mojo_application_bindings',
         'mojo_base.gyp:mojo_common_lib',
         'mojo_base.gyp:mojo_environment_chromium',
@@ -349,6 +352,7 @@
       'sources': [
         'service_manager/background_shell_service_loader.cc',
         'service_manager/background_shell_service_loader.h',
+        'service_manager/service_loader.cc',
         'service_manager/service_loader.h',
         'service_manager/service_manager.cc',
         'service_manager/service_manager.h',
diff --git a/mojo/mojo_examples.gypi b/mojo/mojo_examples.gypi
index 836305c..287901e 100644
--- a/mojo/mojo_examples.gypi
+++ b/mojo/mojo_examples.gypi
@@ -205,6 +205,22 @@
       ],
     },
     {
+      'target_name': 'mojo_content_handler_demo',
+      'type': 'loadable_module',
+      'dependencies': [
+        'mojo_base.gyp:mojo_application_standalone',
+        'mojo_base.gyp:mojo_cpp_bindings',
+        'mojo_base.gyp:mojo_environment_standalone',
+        'mojo_base.gyp:mojo_utility',
+        'mojo_content_handler_bindings',
+        '<(mojo_system_for_loadable_module)',
+      ],
+      'sources': [
+        'examples/content_handler_demo/content_handler_demo.cc',
+        'public/cpp/application/lib/mojo_main_standalone.cc',
+      ],
+    },
+    {
       'target_name': 'package_mojo_wget',
       'variables': {
         'app_name': 'mojo_wget',
diff --git a/mojo/mojo_services.gypi b/mojo/mojo_services.gypi
index 3e07f8e..611aee0 100644
--- a/mojo/mojo_services.gypi
+++ b/mojo/mojo_services.gypi
@@ -365,6 +365,23 @@
       ],
     },
     {
+      # GN version: //mojo/services/public/interfaces/content_handler
+      'target_name': 'mojo_content_handler_bindings',
+      'type': 'static_library',
+      'sources': [
+        'services/public/interfaces/content_handler/content_handler.mojom',
+      ],
+      'includes': [ 'public/tools/bindings/mojom_bindings_generator.gypi' ],
+      'export_dependent_settings': [
+        'mojo_base.gyp:mojo_cpp_bindings',
+      ],
+      'dependencies': [
+        'mojo_base.gyp:mojo_application_bindings',
+        'mojo_base.gyp:mojo_cpp_bindings',
+        'mojo_network_bindings',
+      ],
+    },
+    {
       # GN version: //mojo/services/public/interfaces/network
       'target_name': 'mojo_network_bindings',
       'type': 'static_library',
diff --git a/mojo/service_manager/BUILD.gn b/mojo/service_manager/BUILD.gn
index c526e6d..c7d8790 100644
--- a/mojo/service_manager/BUILD.gn
+++ b/mojo/service_manager/BUILD.gn
@@ -8,6 +8,7 @@ component("service_manager") {
   sources = [
     "background_shell_service_loader.cc",
     "background_shell_service_loader.h",
+    "service_loader.cc",
     "service_loader.h",
     "service_manager.cc",
     "service_manager.h",
@@ -24,6 +25,8 @@ component("service_manager") {
     "//mojo/common",
     "//mojo/environment:chromium",
     "//mojo/public/interfaces/application:application",
+    "//mojo/services/public/interfaces/content_handler:content_handler",
+    "//mojo/services/public/interfaces/network:network",
     "//mojo/system",
   ]
 
diff --git a/mojo/service_manager/background_shell_service_loader.cc b/mojo/service_manager/background_shell_service_loader.cc
index ef97255..d0e5e97 100644
--- a/mojo/service_manager/background_shell_service_loader.cc
+++ b/mojo/service_manager/background_shell_service_loader.cc
@@ -15,10 +15,12 @@ class BackgroundShellServiceLoader::BackgroundLoader {
   explicit BackgroundLoader(ServiceLoader* loader) : loader_(loader) {}
   ~BackgroundLoader() {}
 
-  void LoadService(ServiceManager* manager,
-                   const GURL& url,
-                   ScopedMessagePipeHandle shell_handle) {
-    loader_->LoadService(manager, url, shell_handle.Pass());
+  void Load(ServiceManager* manager,
+            const GURL& url,
+            ScopedMessagePipeHandle shell_handle) {
+    scoped_refptr<LoadCallbacks> callbacks(
+        new ServiceLoader::SimpleLoadCallbacks(shell_handle.Pass()));
+    loader_->Load(manager, url, callbacks);
   }
 
   void OnServiceError(ServiceManager* manager, const GURL& url) {
@@ -47,17 +49,21 @@ BackgroundShellServiceLoader::~BackgroundShellServiceLoader() {
     thread_->Join();
 }
 
-void BackgroundShellServiceLoader::LoadService(
+void BackgroundShellServiceLoader::Load(
     ServiceManager* manager,
     const GURL& url,
-    ScopedMessagePipeHandle shell_handle) {
+    scoped_refptr<LoadCallbacks> callbacks) {
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
+
   if (!thread_) {
-    // TODO(tim): It'd be nice if we could just have each LoadService call
+    // TODO(tim): It'd be nice if we could just have each Load call
     // result in a new thread like DynamicService{Loader, Runner}. But some
     // loaders are creating multiple ApplicationImpls (NetworkServiceLoader)
     // sharing a delegate (etc). So we have to keep it single threaded, wait
     // for the thread to initialize, and post to the TaskRunner for subsequent
-    // LoadService calls for now.
+    // Load calls for now.
     thread_.reset(new base::DelegateSimpleThread(this, thread_name_));
     thread_->Start();
     message_loop_created_.Wait();
@@ -65,7 +71,7 @@ void BackgroundShellServiceLoader::LoadService(
   }
 
   task_runner_->PostTask(FROM_HERE,
-      base::Bind(&BackgroundShellServiceLoader::LoadServiceOnBackgroundThread,
+      base::Bind(&BackgroundShellServiceLoader::LoadOnBackgroundThread,
                  base::Unretained(this), manager, url,
                  base::Owned(
                     new ScopedMessagePipeHandle(shell_handle.Pass()))));
@@ -93,14 +99,14 @@ void BackgroundShellServiceLoader::Run() {
   loader_.reset();
 }
 
-void BackgroundShellServiceLoader::LoadServiceOnBackgroundThread(
+void BackgroundShellServiceLoader::LoadOnBackgroundThread(
       ServiceManager* manager,
       const GURL& url,
       ScopedMessagePipeHandle* shell_handle) {
   DCHECK(task_runner_->RunsTasksOnCurrentThread());
   if (!background_loader_)
     background_loader_ = new BackgroundLoader(loader_.get());
-  background_loader_->LoadService(manager, url, shell_handle->Pass());
+  background_loader_->Load(manager, url, shell_handle->Pass());
 }
 
 void BackgroundShellServiceLoader::OnServiceErrorOnBackgroundThread(
diff --git a/mojo/service_manager/background_shell_service_loader.h b/mojo/service_manager/background_shell_service_loader.h
index 3f4b3fc..a28b33f 100644
--- a/mojo/service_manager/background_shell_service_loader.h
+++ b/mojo/service_manager/background_shell_service_loader.h
@@ -26,9 +26,9 @@ class MOJO_SERVICE_MANAGER_EXPORT BackgroundShellServiceLoader :
   virtual ~BackgroundShellServiceLoader();
 
   // ServiceLoader overrides:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
   virtual void OnServiceError(ServiceManager* manager,
                               const GURL& url) OVERRIDE;
 
@@ -42,10 +42,9 @@ class MOJO_SERVICE_MANAGER_EXPORT BackgroundShellServiceLoader :
   // to |background_loader_| to do the actual loading.
   // TODO: having this code take a |manager| is fragile (as ServiceManager isn't
   // thread safe).
-  void LoadServiceOnBackgroundThread(
-      ServiceManager* manager,
-      const GURL& url,
-      ScopedMessagePipeHandle* shell_handle);
+  void LoadOnBackgroundThread(ServiceManager* manager,
+                              const GURL& url,
+                              ScopedMessagePipeHandle* shell_handle);
   void OnServiceErrorOnBackgroundThread(ServiceManager* manager,
                                         const GURL& url);
   bool quit_on_shutdown_;
diff --git a/mojo/service_manager/background_shell_service_loader_unittest.cc b/mojo/service_manager/background_shell_service_loader_unittest.cc
index 7469b0f..8aeacba 100644
--- a/mojo/service_manager/background_shell_service_loader_unittest.cc
+++ b/mojo/service_manager/background_shell_service_loader_unittest.cc
@@ -16,9 +16,9 @@ class DummyLoader : public ServiceLoader {
   virtual ~DummyLoader() {}
 
   // ServiceLoader overrides:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE {
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
     if (simulate_app_quit_)
       base::MessageLoop::current()->Quit();
   }
@@ -49,7 +49,9 @@ TEST(BackgroundShellServiceLoaderTest, Load) {
   BackgroundShellServiceLoader loader(real_loader.Pass(), "test",
                                       base::MessageLoop::TYPE_DEFAULT);
   MessagePipe dummy;
-  loader.LoadService(NULL, GURL(), dummy.handle0.Pass());
+  scoped_refptr<ServiceLoader::SimpleLoadCallbacks> callbacks(
+      new ServiceLoader::SimpleLoadCallbacks(dummy.handle0.Pass()));
+  loader.Load(NULL, GURL(), callbacks);
 }
 
 }  // namespace mojo
diff --git a/mojo/service_manager/service_loader.cc b/mojo/service_manager/service_loader.cc
new file mode 100644
index 0000000..01c6803
--- /dev/null
+++ b/mojo/service_manager/service_loader.cc
@@ -0,0 +1,29 @@
+// 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 "mojo/service_manager/service_loader.h"
+
+#include "base/logging.h"
+
+namespace mojo {
+
+ServiceLoader::SimpleLoadCallbacks::SimpleLoadCallbacks(
+    ScopedMessagePipeHandle shell_handle)
+    : shell_handle_(shell_handle.Pass()) {
+}
+
+ServiceLoader::SimpleLoadCallbacks::~SimpleLoadCallbacks() {
+}
+
+ScopedMessagePipeHandle
+ServiceLoader::SimpleLoadCallbacks::RegisterApplication() {
+  return shell_handle_.Pass();
+}
+
+void ServiceLoader::SimpleLoadCallbacks::LoadWithContentHandler(
+    const GURL& content_handle_url, URLResponsePtr content) {
+  NOTREACHED();
+}
+
+}  // namespace mojo
diff --git a/mojo/service_manager/service_loader.h b/mojo/service_manager/service_loader.h
index 07be7d9..5c44a53 100644
--- a/mojo/service_manager/service_loader.h
+++ b/mojo/service_manager/service_loader.h
@@ -5,8 +5,10 @@
 #ifndef MOJO_SERVICE_MANAGER_SERVICE_LOADER_H_
 #define MOJO_SERVICE_MANAGER_SERVICE_LOADER_H_
 
+#include "base/memory/ref_counted.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/service_manager/service_manager_export.h"
+#include "mojo/services/public/interfaces/network/url_loader.mojom.h"
 #include "url/gurl.h"
 
 namespace mojo {
@@ -23,10 +25,54 @@ class ServiceManager;
 // apps and services.
 class MOJO_SERVICE_MANAGER_EXPORT ServiceLoader {
  public:
+  class MOJO_SERVICE_MANAGER_EXPORT LoadCallbacks
+      : public base::RefCounted<LoadCallbacks> {
+   public:
+    // Register the requested application with ServiceManager. If the returned
+    // handle is valid, it should be used to implement the mojo::Application
+    // interface.
+    virtual ScopedMessagePipeHandle RegisterApplication() = 0;
+
+    // Load the requested application with a content handler.
+    virtual void LoadWithContentHandler(const GURL& content_handler_url,
+                                        URLResponsePtr response) = 0;
+   protected:
+    friend base::RefCounted<LoadCallbacks>;
+    virtual ~LoadCallbacks() {}
+  };
+
+  // Implements RegisterApplication() by returning a handle that was specified
+  // at construction time. LoadWithContentHandler() is not supported.
+  class MOJO_SERVICE_MANAGER_EXPORT SimpleLoadCallbacks : public LoadCallbacks {
+   public:
+    SimpleLoadCallbacks(ScopedMessagePipeHandle shell_handle);
+    virtual ScopedMessagePipeHandle RegisterApplication() OVERRIDE;
+    virtual void LoadWithContentHandler(const GURL& content_handler_url,
+                                        URLResponsePtr response) OVERRIDE;
+   private:
+    ScopedMessagePipeHandle shell_handle_;
+    virtual ~SimpleLoadCallbacks();
+  };
+
   virtual ~ServiceLoader() {}
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) = 0;
+
+  // Load the application named |url|. Applications can be loaded two ways:
+  //
+  // 1. |url| can refer directly to a Mojo application. In this case, call
+  //    callbacks->RegisterApplication(). The returned handle should be used to
+  //    implement the mojo.Application interface. Note that the returned handle
+  //    can be invalid in the case where the application has already been
+  //    loaded.
+  //
+  // 2. |url| can refer to some content that can be handled by some other Mojo
+  //    application. In this case, call callbacks->LoadWithContentHandler() and
+  //    specify the URL of the application that should handle the content.
+  //    The specified application must implement the mojo.ContentHandler
+  //    interface.
+  virtual void Load(ServiceManager* service_manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) = 0;
+
   virtual void OnServiceError(ServiceManager* manager, const GURL& url) = 0;
 
  protected:
diff --git a/mojo/service_manager/service_manager.cc b/mojo/service_manager/service_manager.cc
index 51efd41..b0ef1e8 100644
--- a/mojo/service_manager/service_manager.cc
+++ b/mojo/service_manager/service_manager.cc
@@ -2,18 +2,21 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include <stdio.h>
-
 #include "mojo/service_manager/service_manager.h"
 
+#include <stdio.h>
+
+#include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/stl_util.h"
 #include "mojo/common/common_type_converters.h"
+#include "mojo/public/cpp/application/connect.h"
 #include "mojo/public/interfaces/application/application.mojom.h"
 #include "mojo/public/interfaces/application/shell.mojom.h"
 #include "mojo/service_manager/service_loader.h"
+#include "mojo/services/public/interfaces/content_handler/content_handler.mojom.h"
 
 namespace mojo {
 
@@ -33,7 +36,52 @@ class StubServiceProvider : public InterfaceImpl<ServiceProvider> {
       ScopedMessagePipeHandle client_handle) MOJO_OVERRIDE {}
 };
 
-}
+}  // namespace
+
+class ServiceManager::LoadCallbacksImpl : public ServiceLoader::LoadCallbacks {
+ public:
+  LoadCallbacksImpl(base::WeakPtr<ServiceManager> manager,
+                    const GURL& requested_url,
+                    const GURL& requestor_url,
+                    ServiceProviderPtr service_provider)
+      : manager_(manager),
+        requested_url_(requested_url),
+        requestor_url_(requestor_url),
+        service_provider_(service_provider.Pass()) {
+  }
+
+ private:
+  virtual ~LoadCallbacksImpl() {
+  }
+
+  // LoadCallbacks implementation
+  virtual ScopedMessagePipeHandle RegisterApplication() OVERRIDE {
+    ScopedMessagePipeHandle shell_handle;
+    if (manager_) {
+      manager_->RegisterLoadedApplication(requested_url_,
+                                          requestor_url_,
+                                          service_provider_.Pass(),
+                                          &shell_handle);
+    }
+    return shell_handle.Pass();
+  }
+
+  virtual void LoadWithContentHandler(const GURL& content_handler_url,
+                                      URLResponsePtr content) OVERRIDE {
+    if (manager_) {
+      manager_->LoadWithContentHandler(requested_url_,
+                                       requestor_url_,
+                                       content_handler_url,
+                                       content.Pass(),
+                                       service_provider_.Pass());
+    }
+  }
+
+  base::WeakPtr<ServiceManager> manager_;
+  GURL requested_url_;
+  GURL requestor_url_;
+  ServiceProviderPtr service_provider_;
+};
 
 class ServiceManager::ShellImpl : public InterfaceImpl<Shell> {
  public:
@@ -76,6 +124,21 @@ class ServiceManager::ShellImpl : public InterfaceImpl<Shell> {
   DISALLOW_COPY_AND_ASSIGN(ShellImpl);
 };
 
+struct ServiceManager::ContentHandlerConnection {
+  ContentHandlerConnection(ServiceManager* manager,
+                           const GURL& content_handler_url) {
+    ServiceProviderPtr service_provider;
+    BindToProxy(&service_provider_impl, &service_provider);
+    manager->ConnectToApplication(content_handler_url,
+                                  GURL(),
+                                  service_provider.Pass());
+    mojo::ConnectToService(service_provider_impl.client(), &content_handler);
+  }
+
+  StubServiceProvider service_provider_impl;
+  ContentHandlerPtr content_handler;
+};
+
 // static
 ServiceManager::TestAPI::TestAPI(ServiceManager* manager) : manager_(manager) {
 }
@@ -92,10 +155,13 @@ bool ServiceManager::TestAPI::HasFactoryForURL(const GURL& url) const {
          manager_->url_to_shell_impl_.end();
 }
 
-ServiceManager::ServiceManager() : interceptor_(NULL) {
+ServiceManager::ServiceManager()
+    : interceptor_(NULL),
+      weak_ptr_factory_(this) {
 }
 
 ServiceManager::~ServiceManager() {
+  STLDeleteValues(&url_to_content_handler_);
   TerminateShellConnections();
   STLDeleteValues(&url_to_loader_);
   STLDeleteValues(&scheme_to_loader_);
@@ -117,15 +183,24 @@ void ServiceManager::ConnectToApplication(const GURL& url,
                                           const GURL& requestor_url,
                                           ServiceProviderPtr service_provider) {
   URLToShellImplMap::const_iterator shell_it = url_to_shell_impl_.find(url);
-  ShellImpl* shell_impl;
   if (shell_it != url_to_shell_impl_.end()) {
-    shell_impl = shell_it->second;
-  } else {
-    MessagePipe pipe;
-    GetLoaderForURL(url)->LoadService(this, url, pipe.handle0.Pass());
-    shell_impl = WeakBindToPipe(new ShellImpl(this, url), pipe.handle1.Pass());
-    url_to_shell_impl_[url] = shell_impl;
+    ConnectToClient(shell_it->second, url, requestor_url,
+                    service_provider.Pass());
+    return;
   }
+
+  scoped_refptr<LoadCallbacksImpl> callbacks(
+      new LoadCallbacksImpl(weak_ptr_factory_.GetWeakPtr(),
+                            url,
+                            requestor_url,
+                            service_provider.Pass()));
+  GetLoaderForURL(url)->Load(this, url, callbacks);
+}
+
+void ServiceManager::ConnectToClient(ShellImpl* shell_impl,
+                                     const GURL& url,
+                                     const GURL& requestor_url,
+                                     ServiceProviderPtr service_provider) {
   if (interceptor_) {
     shell_impl->ConnectToClient(
         requestor_url,
@@ -135,6 +210,48 @@ void ServiceManager::ConnectToApplication(const GURL& url,
   }
 }
 
+void ServiceManager::RegisterLoadedApplication(
+    const GURL& url,
+    const GURL& requestor_url,
+    ServiceProviderPtr service_provider,
+    ScopedMessagePipeHandle* shell_handle) {
+  ShellImpl* shell_impl = NULL;
+  URLToShellImplMap::iterator iter = url_to_shell_impl_.find(url);
+  if (iter != url_to_shell_impl_.end()) {
+    // This can happen because services are loaded asynchronously. So if we get
+    // two requests for the same service close to each other, we might get here
+    // and find that we already have it.
+    shell_impl = iter->second;
+  } else {
+    MessagePipe pipe;
+    shell_impl = WeakBindToPipe(new ShellImpl(this, url), pipe.handle1.Pass());
+    url_to_shell_impl_[url] = shell_impl;
+    *shell_handle = pipe.handle0.Pass();
+  }
+
+  ConnectToClient(shell_impl, url, requestor_url, service_provider.Pass());
+}
+
+void ServiceManager::LoadWithContentHandler(
+    const GURL& content_url,
+    const GURL& requestor_url,
+    const GURL& content_handler_url,
+    URLResponsePtr content,
+    ServiceProviderPtr service_provider) {
+  ContentHandlerConnection* connection = NULL;
+  URLToContentHandlerMap::iterator iter =
+      url_to_content_handler_.find(content_handler_url);
+  if (iter != url_to_content_handler_.end()) {
+    connection = iter->second;
+  } else {
+    connection = new ContentHandlerConnection(this, content_handler_url);
+    url_to_content_handler_[content_handler_url] = connection;
+  }
+  connection->content_handler->OnConnect(content_url.spec(),
+                                         content.Pass(),
+                                         service_provider.Pass());
+}
+
 void ServiceManager::SetLoaderForURL(scoped_ptr<ServiceLoader> loader,
                                      const GURL& url) {
   URLToLoaderMap::iterator it = url_to_loader_.find(url);
diff --git a/mojo/service_manager/service_manager.h b/mojo/service_manager/service_manager.h
index 69ebda6..76cda8c 100644
--- a/mojo/service_manager/service_manager.h
+++ b/mojo/service_manager/service_manager.h
@@ -10,6 +10,7 @@
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
 #include "mojo/public/interfaces/application/service_provider.mojom.h"
 #include "mojo/service_manager/service_loader.h"
 #include "mojo/service_manager/service_manager_export.h"
@@ -87,10 +88,30 @@ class MOJO_SERVICE_MANAGER_EXPORT ServiceManager {
   void TerminateShellConnections();
 
  private:
+  struct ContentHandlerConnection;
+  class LoadCallbacksImpl;
   class ShellImpl;
+
   typedef std::map<std::string, ServiceLoader*> SchemeToLoaderMap;
   typedef std::map<GURL, ServiceLoader*> URLToLoaderMap;
   typedef std::map<GURL, ShellImpl*> URLToShellImplMap;
+  typedef std::map<GURL, ContentHandlerConnection*> URLToContentHandlerMap;
+
+  void ConnectToClient(ShellImpl* shell_impl,
+                       const GURL& url,
+                       const GURL& requestor_url,
+                       ServiceProviderPtr service_provider);
+
+  void RegisterLoadedApplication(const GURL& service_url,
+                                 const GURL& requestor_url,
+                                 ServiceProviderPtr service_provider,
+                                 ScopedMessagePipeHandle* shell_handle);
+
+  void LoadWithContentHandler(const GURL& content_url,
+                              const GURL& requestor_url,
+                              const GURL& content_handler_url,
+                              URLResponsePtr content,
+                              ServiceProviderPtr service_provider);
 
   // Returns the Loader to use for a url (using default if not overridden.)
   // The preference is to use a loader that's been specified for an url first,
@@ -107,6 +128,9 @@ class MOJO_SERVICE_MANAGER_EXPORT ServiceManager {
   Interceptor* interceptor_;
 
   URLToShellImplMap url_to_shell_impl_;
+  URLToContentHandlerMap url_to_content_handler_;
+
+  base::WeakPtrFactory<ServiceManager> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceManager);
 };
diff --git a/mojo/service_manager/service_manager_unittest.cc b/mojo/service_manager/service_manager_unittest.cc
index f42113f..0f984c17 100644
--- a/mojo/service_manager/service_manager_unittest.cc
+++ b/mojo/service_manager/service_manager_unittest.cc
@@ -118,12 +118,12 @@ class TestServiceLoader : public ServiceLoader,
 
  private:
   // ServiceLoader implementation.
-  virtual void LoadService(
-      ServiceManager* manager,
-      const GURL& url,
-      ScopedMessagePipeHandle service_provider_handle) OVERRIDE {
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
     ++num_loads_;
-    test_app_.reset(new ApplicationImpl(this, service_provider_handle.Pass()));
+    test_app_.reset(
+        new ApplicationImpl(this, callbacks->RegisterApplication().Pass()));
   }
 
   virtual void OnServiceError(ServiceManager* manager,
@@ -332,11 +332,11 @@ class Tester : public ApplicationDelegate,
   virtual ~Tester() {}
 
  private:
-  virtual void LoadService(
-      ServiceManager* manager,
-      const GURL& url,
-      ScopedMessagePipeHandle shell_handle) OVERRIDE {
-    app_.reset(new ApplicationImpl(this, shell_handle.Pass()));
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
+    app_.reset(
+        new ApplicationImpl(this, callbacks->RegisterApplication().Pass()));
   }
 
   virtual void OnServiceError(ServiceManager* manager,
diff --git a/mojo/services/BUILD.gn b/mojo/services/BUILD.gn
index 09753e07..619a9f9 100644
--- a/mojo/services/BUILD.gn
+++ b/mojo/services/BUILD.gn
@@ -6,6 +6,7 @@ group("services") {
   deps = [
     "//mojo/services/dbus_echo:bindings",
     "//mojo/services/gles2:bindings",
+    "//mojo/services/public/interfaces/content_handler",
     "//mojo/services/public/interfaces/input_events",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/public/interfaces/native_viewport",
diff --git a/mojo/services/public/cpp/view_manager/tests/view_manager_unittest.cc b/mojo/services/public/cpp/view_manager/tests/view_manager_unittest.cc
index f56a060..7afde90 100644
--- a/mojo/services/public/cpp/view_manager/tests/view_manager_unittest.cc
+++ b/mojo/services/public/cpp/view_manager/tests/view_manager_unittest.cc
@@ -55,9 +55,12 @@ class ConnectServiceLoader : public ServiceLoader,
 
  private:
   // Overridden from ServiceLoader:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE {
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
+    ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+    if (!shell_handle.is_valid())
+      return;
     scoped_ptr<ApplicationImpl> app(new ApplicationImpl(this,
                                                         shell_handle.Pass()));
     apps_.push_back(app.release());
diff --git a/mojo/services/public/interfaces/content_handler/BUILD.gn b/mojo/services/public/interfaces/content_handler/BUILD.gn
new file mode 100644
index 0000000..c72cc9a
--- /dev/null
+++ b/mojo/services/public/interfaces/content_handler/BUILD.gn
@@ -0,0 +1,17 @@
+# 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.
+
+import("//mojo/public/tools/bindings/mojom.gni")
+
+# GYP version: mojo/mojo_services.gypi:mojo_content_handler_bindings
+mojom("content_handler") {
+  sources = [
+    "content_handler.mojom",
+  ]
+
+  deps = [
+    "//mojo/public/interfaces/application",
+    "//mojo/services/public/interfaces/network",
+  ]
+}
diff --git a/mojo/services/public/interfaces/content_handler/content_handler.mojom b/mojo/services/public/interfaces/content_handler/content_handler.mojom
new file mode 100644
index 0000000..6c07580
--- /dev/null
+++ b/mojo/services/public/interfaces/content_handler/content_handler.mojom
@@ -0,0 +1,16 @@
+// 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.
+
+import "mojo/public/interfaces/application/service_provider.mojom"
+import "mojo/services/public/interfaces/network/url_loader.mojom"
+
+module mojo {
+
+interface ContentHandler {
+  OnConnect(string url,
+            URLResponse url_response,
+            ServiceProvider service_provider);
+};
+
+}
diff --git a/mojo/services/view_manager/view_manager_unittest.cc b/mojo/services/view_manager/view_manager_unittest.cc
index 3d24a18..8c3e13f 100644
--- a/mojo/services/view_manager/view_manager_unittest.cc
+++ b/mojo/services/view_manager/view_manager_unittest.cc
@@ -386,9 +386,12 @@ class EmbedServiceLoader : public ServiceLoader,
   virtual ~EmbedServiceLoader() {}
 
   // ServiceLoader implementation:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE {
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
+    ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+    if (!shell_handle.is_valid())
+      return;
     scoped_ptr<ApplicationImpl> app(new ApplicationImpl(this,
                                                         shell_handle.Pass()));
     apps_.push_back(app.release());
diff --git a/mojo/services/window_manager/window_manager_api_unittest.cc b/mojo/services/window_manager/window_manager_api_unittest.cc
index 4450c3b..b557bc9 100644
--- a/mojo/services/window_manager/window_manager_api_unittest.cc
+++ b/mojo/services/window_manager/window_manager_api_unittest.cc
@@ -132,9 +132,12 @@ class TestServiceLoader : public ServiceLoader,
 
  private:
   // Overridden from ServiceLoader:
-  virtual void LoadService(ServiceManager* service_manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) MOJO_OVERRIDE {
+  virtual void Load(ServiceManager* service_manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) MOJO_OVERRIDE {
+    ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+    if (!shell_handle.is_valid())
+      return;
     scoped_ptr<ApplicationImpl> app(
         new ApplicationImpl(this, shell_handle.Pass()));
     apps_.push_back(app.release());
diff --git a/mojo/shell/context.cc b/mojo/shell/context.cc
index 76cc7d6..a6dea44 100644
--- a/mojo/shell/context.cc
+++ b/mojo/shell/context.cc
@@ -4,10 +4,13 @@
 
 #include "mojo/shell/context.h"
 
+#include <vector>
+
 #include "build/build_config.h"
 #include "base/command_line.h"
 #include "base/lazy_instance.h"
 #include "base/memory/scoped_vector.h"
+#include "base/strings/string_split.h"
 #include "mojo/embedder/embedder.h"
 #include "mojo/gles2/gles2_support_impl.h"
 #include "mojo/public/cpp/application/application_impl.h"
@@ -61,6 +64,32 @@ class Setup {
 
 static base::LazyInstance<Setup>::Leaky setup = LAZY_INSTANCE_INITIALIZER;
 
+void InitContentHandlers(DynamicServiceLoader* loader,
+                         base::CommandLine* command_line) {
+  std::string handlers_spec = command_line->GetSwitchValueASCII(
+      switches::kContentHandlers);
+  if (handlers_spec.empty())
+    return;
+
+  std::vector<std::string> parts;
+  base::SplitString(handlers_spec, ',', &parts);
+  if (parts.size() % 2 != 0) {
+    LOG(ERROR) << "Invalid value for switch " << switches::kContentHandlers
+               << ": must be a comma-separated list of mimetype/url pairs.";
+    return;
+  }
+
+  for (size_t i = 0; i < parts.size(); i += 2) {
+    GURL url(parts[i + 1]);
+    if (!url.is_valid()) {
+      LOG(ERROR) << "Invalid value for switch " << switches::kContentHandlers
+                 << ": '" << parts[i + 1] << "' is not a valid URL.";
+      return;
+    }
+    loader->RegisterContentHandler(parts[i], url);
+  }
+}
+
 }  // namespace
 
 class Context::NativeViewportServiceLoader : public ServiceLoader {
@@ -69,10 +98,12 @@ class Context::NativeViewportServiceLoader : public ServiceLoader {
   virtual ~NativeViewportServiceLoader() {}
 
  private:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE {
-    app_.reset(services::CreateNativeViewportService(shell_handle.Pass()));
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE {
+    ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+    if (shell_handle.is_valid())
+      app_.reset(services::CreateNativeViewportService(shell_handle.Pass()));
   }
 
   virtual void OnServiceError(ServiceManager* manager,
@@ -95,16 +126,19 @@ void Context::Init() {
   for (size_t i = 0; i < arraysize(kLocalMojoURLs); ++i)
     mojo_url_resolver_.AddLocalFileMapping(GURL(kLocalMojoURLs[i]));
 
-  base::CommandLine* cmdline = base::CommandLine::ForCurrentProcess();
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   scoped_ptr<DynamicServiceRunnerFactory> runner_factory;
-  if (cmdline->HasSwitch(switches::kEnableMultiprocess))
+  if (command_line->HasSwitch(switches::kEnableMultiprocess))
     runner_factory.reset(new OutOfProcessDynamicServiceRunnerFactory());
   else
     runner_factory.reset(new InProcessDynamicServiceRunnerFactory());
 
+  DynamicServiceLoader* dynamic_service_loader =
+      new DynamicServiceLoader(this, runner_factory.Pass());
+  InitContentHandlers(dynamic_service_loader, command_line);
   service_manager_.set_default_loader(
-      scoped_ptr<ServiceLoader>(
-          new DynamicServiceLoader(this, runner_factory.Pass())));
+      scoped_ptr<ServiceLoader>(dynamic_service_loader));
+
   // The native viewport service synchronously waits for certain messages. If we
   // don't run it on its own thread we can easily deadlock. Long term native
   // viewport should run its own process so that this isn't an issue.
@@ -140,9 +174,9 @@ void Context::Init() {
       "dbus");
 #endif  // defined(OS_LINUX)
 
-  if (cmdline->HasSwitch(switches::kSpy)) {
-    spy_.reset(new mojo::Spy(&service_manager_,
-                             cmdline->GetSwitchValueASCII(switches::kSpy)));
+  if (command_line->HasSwitch(switches::kSpy)) {
+    spy_.reset(new mojo::Spy(
+        &service_manager_, command_line->GetSwitchValueASCII(switches::kSpy)));
   }
 
 #if defined(OS_ANDROID)
diff --git a/mojo/shell/dbus_service_loader_linux.cc b/mojo/shell/dbus_service_loader_linux.cc
index af4e0d4..934637e 100644
--- a/mojo/shell/dbus_service_loader_linux.cc
+++ b/mojo/shell/dbus_service_loader_linux.cc
@@ -150,9 +150,15 @@ DBusServiceLoader::~DBusServiceLoader() {
   DCHECK(url_to_load_context_.empty());
 }
 
-void DBusServiceLoader::LoadService(ServiceManager* manager,
-                                    const GURL& url,
-                                    ScopedMessagePipeHandle shell_handle) {
+void DBusServiceLoader::Load(ServiceManager* manager,
+                             const GURL& url,
+                             scoped_refptr<LoadCallbacks> callbacks) {
+  // TODO(aa): This could be delayed until later, when we know that loading is
+  // going to succeed.
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
+
   DCHECK(url.SchemeIs("dbus"));
   DCHECK(url_to_load_context_.find(url) == url_to_load_context_.end());
   url_to_load_context_[url] =
diff --git a/mojo/shell/dbus_service_loader_linux.h b/mojo/shell/dbus_service_loader_linux.h
index a24af5f..1aae927 100644
--- a/mojo/shell/dbus_service_loader_linux.h
+++ b/mojo/shell/dbus_service_loader_linux.h
@@ -61,9 +61,9 @@ class DBusServiceLoader : public ServiceLoader {
   // the name "org.chromium.EchoService" and invoke the method
   // "org.chromium.Mojo.ConnectChannel" on the object exported at
   // "/org/chromium/MojoImpl".
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
 
   virtual void OnServiceError(ServiceManager* manager, const GURL& url)
       OVERRIDE;
diff --git a/mojo/shell/dynamic_service_loader.cc b/mojo/shell/dynamic_service_loader.cc
index a8e6914..73dd6dd 100644
--- a/mojo/shell/dynamic_service_loader.cc
+++ b/mojo/shell/dynamic_service_loader.cc
@@ -20,122 +20,15 @@
 
 namespace mojo {
 namespace shell {
-namespace {
-
-class Loader {
- public:
-  explicit Loader(scoped_ptr<DynamicServiceRunner> runner)
-      : runner_(runner.Pass()) {
-  }
-
-  virtual void Start(const GURL& url,
-                     ScopedMessagePipeHandle service_handle,
-                     Context* context) = 0;
-
-  void StartService(const base::FilePath& path,
-                    ScopedMessagePipeHandle service_handle,
-                    bool path_is_valid) {
-    if (path_is_valid) {
-      runner_->Start(path, service_handle.Pass(),
-                     base::Bind(&Loader::AppCompleted, base::Unretained(this)));
-    } else {
-      AppCompleted();
-    }
-  }
-
- protected:
-  virtual ~Loader() {}
-
- private:
-  void AppCompleted() {
-    delete this;
-  }
-
-  scoped_ptr<DynamicServiceRunner> runner_;
-};
-
-// For loading services via file:// URLs.
-class LocalLoader : public Loader {
- public:
-  explicit LocalLoader(scoped_ptr<DynamicServiceRunner> runner)
-      : Loader(runner.Pass()) {
-  }
-
-  virtual void Start(const GURL& url,
-                     ScopedMessagePipeHandle service_handle,
-                     Context* context) OVERRIDE {
-    base::FilePath path;
-    net::FileURLToFilePath(url, &path);
-
-    // Complete asynchronously for consistency with NetworkServiceLoader.
-    base::MessageLoop::current()->PostTask(
-        FROM_HERE,
-        base::Bind(&Loader::StartService,
-                   base::Unretained(this),
-                   path,
-                   base::Passed(&service_handle),
-                   base::PathExists(path)));
-  }
-};
-
-// For loading services via the network stack.
-class NetworkLoader : public Loader {
- public:
-  explicit NetworkLoader(scoped_ptr<DynamicServiceRunner> runner,
-                         NetworkService* network_service)
-      : Loader(runner.Pass()) {
-    network_service->CreateURLLoader(Get(&url_loader_));
-  }
-
-  virtual void Start(const GURL& url,
-                    ScopedMessagePipeHandle service_handle,
-                    Context* context) OVERRIDE {
-    service_handle_ = service_handle.Pass();
-    context_ = context;
-
-    URLRequestPtr request(URLRequest::New());
-    request->url = String::From(url);
-    request->auto_follow_redirects = true;
-
-    if (base::CommandLine::ForCurrentProcess()->HasSwitch(
-            switches::kDisableCache)) {
-      request->bypass_cache = true;
-    }
-
-    url_loader_->Start(request.Pass(),
-                       base::Bind(&NetworkLoader::OnReceivedResponse,
-                                  base::Unretained(this)));
-  }
-
- private:
-  virtual ~NetworkLoader() {
-    if (!file_.empty())
-      base::DeleteFile(file_, false);
-  }
 
-  void OnReceivedResponse(URLResponsePtr response) {
-    if (response->error) {
-      LOG(ERROR) << "Error (" << response->error->code << ": "
-                 << response->error->description << ") while fetching "
-                 << response->url;
-    }
-
-    base::CreateTemporaryFile(&file_);
-    common::CopyToFile(response->body.Pass(),
-                       file_,
-                       context_->task_runners()->blocking_pool(),
-                       base::Bind(&Loader::StartService,
-                                  base::Unretained(this),
-                                  file_,
-                                  base::Passed(&service_handle_)));
-  }
+namespace {
 
-  Context* context_;
-  NetworkServicePtr network_service_;
-  URLLoaderPtr url_loader_;
-  ScopedMessagePipeHandle service_handle_;
-  base::FilePath file_;
-};
+void RunLibraryComplete(DynamicServiceRunner* runner,
+                        const base::FilePath& temp_file) {
+  delete runner;
+  if (!temp_file.empty())
+    base::DeleteFile(temp_file, false);
+}
 
 }  // namespace
 
@@ -143,17 +36,22 @@ DynamicServiceLoader::DynamicServiceLoader(
     Context* context,
     scoped_ptr<DynamicServiceRunnerFactory> runner_factory)
     : context_(context),
-      runner_factory_(runner_factory.Pass()) {
+      runner_factory_(runner_factory.Pass()),
+      weak_ptr_factory_(this) {
 }
 
 DynamicServiceLoader::~DynamicServiceLoader() {
 }
 
-void DynamicServiceLoader::LoadService(ServiceManager* manager,
-                                       const GURL& url,
-                                       ScopedMessagePipeHandle shell_handle) {
-  scoped_ptr<DynamicServiceRunner> runner = runner_factory_->Create(context_);
+void DynamicServiceLoader::RegisterContentHandler(
+    const std::string& mime_type,
+    const GURL& content_handler_url) {
+  mime_type_to_url_[mime_type] = content_handler_url;
+}
 
+void DynamicServiceLoader::Load(ServiceManager* manager,
+                                const GURL& url,
+                                scoped_refptr<LoadCallbacks> callbacks) {
   GURL resolved_url;
   if (url.SchemeIs("mojo")) {
     resolved_url = context_->mojo_url_resolver()->Resolve(url);
@@ -161,18 +59,109 @@ void DynamicServiceLoader::LoadService(ServiceManager* manager,
     resolved_url = url;
   }
 
-  Loader* loader;
-  if (resolved_url.SchemeIsFile()) {
-    loader = new LocalLoader(runner.Pass());
-  } else {
-    if (!network_service_) {
-      context_->service_manager()->ConnectToService(
-          GURL("mojo:mojo_network_service"),
-          &network_service_);
-    }
-    loader = new NetworkLoader(runner.Pass(), network_service_.get());
+  if (resolved_url.SchemeIsFile())
+    LoadLocalService(resolved_url, callbacks);
+  else
+    LoadNetworkService(resolved_url, callbacks);
+}
+
+void DynamicServiceLoader::LoadLocalService(
+    const GURL& resolved_url,
+    scoped_refptr<LoadCallbacks> callbacks) {
+  base::FilePath path;
+  net::FileURLToFilePath(resolved_url, &path);
+  const bool kDeleteFileAfter = false;
+
+  // Async for consistency with network case.
+  base::MessageLoop::current()->PostTask(
+      FROM_HERE,
+      base::Bind(&DynamicServiceLoader::RunLibrary,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 path,
+                 callbacks,
+                 kDeleteFileAfter,
+                 base::PathExists(path)));
+}
+
+void DynamicServiceLoader::LoadNetworkService(
+    const GURL& resolved_url,
+    scoped_refptr<LoadCallbacks> callbacks) {
+  if (!network_service_) {
+    context_->service_manager()->ConnectToService(
+        GURL("mojo:mojo_network_service"),
+        &network_service_);
   }
-  loader->Start(resolved_url, shell_handle.Pass(), context_);
+  if (!url_loader_)
+    network_service_->CreateURLLoader(Get(&url_loader_));
+
+  URLRequestPtr request(URLRequest::New());
+  request->url = String::From(resolved_url);
+  request->auto_follow_redirects = true;
+
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kDisableCache)) {
+    request->bypass_cache = true;
+  }
+
+  url_loader_->Start(
+      request.Pass(),
+      base::Bind(&DynamicServiceLoader::OnLoadNetworkServiceComplete,
+                 weak_ptr_factory_.GetWeakPtr(),
+                 callbacks));
+}
+
+void DynamicServiceLoader::OnLoadNetworkServiceComplete(
+    scoped_refptr<LoadCallbacks> callbacks, URLResponsePtr response) {
+  if (response->error) {
+    LOG(ERROR) << "Error (" << response->error->code << ": "
+               << response->error->description << ") while fetching "
+               << response->url;
+  }
+
+  MimeTypeToURLMap::iterator iter =
+      mime_type_to_url_.find(response->mime_type);
+  if (iter != mime_type_to_url_.end()) {
+    callbacks->LoadWithContentHandler(iter->second, response.Pass());
+    return;
+  }
+
+  base::FilePath file;
+  base::CreateTemporaryFile(&file);
+
+  const bool kDeleteFileAfter = true;
+  common::CopyToFile(response->body.Pass(),
+                     file,
+                     context_->task_runners()->blocking_pool(),
+                     base::Bind(&DynamicServiceLoader::RunLibrary,
+                                weak_ptr_factory_.GetWeakPtr(),
+                                file,
+                                callbacks,
+                                kDeleteFileAfter));
+}
+
+void DynamicServiceLoader::RunLibrary(const base::FilePath& path,
+                                      scoped_refptr<LoadCallbacks> callbacks,
+                                      bool delete_file_after,
+                                      bool path_exists) {
+  // TODO(aa): We need to create a runner, even if we're not going to use it,
+  // because it getting destroyed is what causes shell to shut down. If we don't
+  // create this, in the case where shell never successfully creates even one
+  // app, then shell will never shut down, because no runners are ever
+  // destroyed.
+  scoped_ptr<DynamicServiceRunner> runner(runner_factory_->Create(context_));
+  if (!path_exists)
+    return;
+
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
+
+  DynamicServiceRunner* runner_raw = runner.release();
+  runner_raw->Start(path,
+                    shell_handle.Pass(),
+                    base::Bind(&RunLibraryComplete,
+                               base::Unretained(runner_raw),
+                               delete_file_after ? path : base::FilePath()));
 }
 
 void DynamicServiceLoader::OnServiceError(ServiceManager* manager,
diff --git a/mojo/shell/dynamic_service_loader.h b/mojo/shell/dynamic_service_loader.h
index 72bf093..0db2284 100644
--- a/mojo/shell/dynamic_service_loader.h
+++ b/mojo/shell/dynamic_service_loader.h
@@ -8,6 +8,7 @@
 #include <map>
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "mojo/public/cpp/system/core.h"
 #include "mojo/service_manager/service_loader.h"
 #include "mojo/services/public/interfaces/network/network_service.mojom.h"
@@ -30,17 +31,36 @@ class DynamicServiceLoader : public ServiceLoader {
                        scoped_ptr<DynamicServiceRunnerFactory> runner_factory);
   virtual ~DynamicServiceLoader();
 
+  void RegisterContentHandler(const std::string& mime_type,
+                              const GURL& content_handler_url);
+
   // ServiceLoader methods:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle service_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
   virtual void OnServiceError(ServiceManager* manager, const GURL& url)
       OVERRIDE;
 
  private:
+  typedef std::map<std::string, GURL> MimeTypeToURLMap;
+
+  void LoadLocalService(const GURL& resolved_url,
+                        scoped_refptr<LoadCallbacks> callbacks);
+  void LoadNetworkService(const GURL& resolved_url,
+                          scoped_refptr<LoadCallbacks> callbacks);
+  void OnLoadNetworkServiceComplete(scoped_refptr<LoadCallbacks> callbacks,
+                                    URLResponsePtr url_response);
+  void RunLibrary(const base::FilePath& response_file,
+                  scoped_refptr<LoadCallbacks> callbacks,
+                  bool delete_file_after,
+                  bool response_path_exists);
+
   Context* const context_;
   scoped_ptr<DynamicServiceRunnerFactory> runner_factory_;
   NetworkServicePtr network_service_;
+  URLLoaderPtr url_loader_;
+  MimeTypeToURLMap mime_type_to_url_;
+  base::WeakPtrFactory<DynamicServiceLoader> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DynamicServiceLoader);
 };
diff --git a/mojo/shell/dynamic_service_loader_unittest.cc b/mojo/shell/dynamic_service_loader_unittest.cc
index f70d115..915bcf1 100644
--- a/mojo/shell/dynamic_service_loader_unittest.cc
+++ b/mojo/shell/dynamic_service_loader_unittest.cc
@@ -73,7 +73,9 @@ TEST_F(DynamicServiceLoaderTest, DoesNotExist) {
   base::FilePath nonexistent_file(FILE_PATH_LITERAL("nonexistent.txt"));
   GURL url(net::FilePathToFileURL(temp_dir.path().Append(nonexistent_file)));
   MessagePipe pipe;
-  loader_->LoadService(context_.service_manager(), url, pipe.handle0.Pass());
+  scoped_refptr<ServiceLoader::SimpleLoadCallbacks> callbacks(
+      new ServiceLoader::SimpleLoadCallbacks(pipe.handle0.Pass()));
+  loader_->Load(context_.service_manager(), url, callbacks);
   loop_.Run();
   EXPECT_FALSE(state_.runner_was_started);
   EXPECT_TRUE(state_.runner_was_destroyed);
diff --git a/mojo/shell/network_service_loader.cc b/mojo/shell/network_service_loader.cc
index 9f8f87f..8e5cff2 100644
--- a/mojo/shell/network_service_loader.cc
+++ b/mojo/shell/network_service_loader.cc
@@ -29,10 +29,13 @@ NetworkServiceLoader::NetworkServiceLoader() {
 NetworkServiceLoader::~NetworkServiceLoader() {
 }
 
-void NetworkServiceLoader::LoadService(
-    ServiceManager* manager,
-    const GURL& url,
-    ScopedMessagePipeHandle shell_handle) {
+void NetworkServiceLoader::Load(ServiceManager* manager,
+                                const GURL& url,
+                                scoped_refptr<LoadCallbacks> callbacks) {
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
+
   uintptr_t key = reinterpret_cast<uintptr_t>(manager);
   if (apps_.find(key) == apps_.end()) {
     scoped_ptr<ApplicationImpl> app(
diff --git a/mojo/shell/network_service_loader.h b/mojo/shell/network_service_loader.h
index 2184072..0eab765 100644
--- a/mojo/shell/network_service_loader.h
+++ b/mojo/shell/network_service_loader.h
@@ -31,10 +31,9 @@ class NetworkServiceLoader : public ServiceLoader,
 
  private:
   // ServiceLoader overrides:
-  virtual void LoadService(
-      ServiceManager* manager,
-      const GURL& url,
-      ScopedMessagePipeHandle shell_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
   virtual void OnServiceError(ServiceManager* manager,
                               const GURL& url) OVERRIDE;
 
diff --git a/mojo/shell/switches.cc b/mojo/shell/switches.cc
index c597218..cf3697f 100644
--- a/mojo/shell/switches.cc
+++ b/mojo/shell/switches.cc
@@ -10,6 +10,10 @@ namespace switches {
 // |ChildProcess::Type|).
 const char kChildProcessType[] = "child-process-type";
 
+// Comma separated list like:
+// text/html,mojo://mojo_html_viewer,application/bravo,https://abarth.com/bravo
+const char kContentHandlers[] = "content-handlers";
+
 // Force dynamically loaded apps / services to be loaded irrespective of cache
 // instructions.
 const char kDisableCache[] = "disable-cache";
diff --git a/mojo/shell/switches.h b/mojo/shell/switches.h
index a1d4ac5..d2271cf 100644
--- a/mojo/shell/switches.h
+++ b/mojo/shell/switches.h
@@ -10,6 +10,7 @@ namespace switches {
 // All switches in alphabetical order. The switches should be documented
 // alongside the definition of their values in the .cc file.
 extern const char kChildProcessType[];
+extern const char kContentHandlers[];
 extern const char kDisableCache[];
 extern const char kEnableMultiprocess[];
 extern const char kOrigin[];
diff --git a/mojo/shell/ui_service_loader_android.cc b/mojo/shell/ui_service_loader_android.cc
index 3960858..e2f77464b 100644
--- a/mojo/shell/ui_service_loader_android.cc
+++ b/mojo/shell/ui_service_loader_android.cc
@@ -15,10 +15,12 @@ class UIServiceLoader::UILoader {
   explicit UILoader(ServiceLoader* loader) : loader_(loader) {}
   ~UILoader() {}
 
-  void LoadService(ServiceManager* manager,
-                   const GURL& url,
-                   ScopedMessagePipeHandle shell_handle) {
-    loader_->LoadService(manager, url, shell_handle.Pass());
+  void Load(ServiceManager* manager,
+            const GURL& url,
+            ScopedMessagePipeHandle shell_handle) {
+    scoped_refptr<LoadCallbacks> callbacks(
+        new ServiceLoader::SimpleLoadCallbacks(shell_handle.Pass()));
+    loader_->Load(manager, url, callbacks);
   }
 
   void OnServiceError(ServiceManager* manager, const GURL& url) {
@@ -42,17 +44,20 @@ UIServiceLoader::~UIServiceLoader() {
       base::Bind(&UIServiceLoader::ShutdownOnUIThread, base::Unretained(this)));
 }
 
-void UIServiceLoader::LoadService(ServiceManager* manager,
-                                  const GURL& url,
-                                  ScopedMessagePipeHandle shell_handle) {
+void UIServiceLoader::Load(ServiceManager* manager,
+                           const GURL& url,
+                           scoped_refptr<LoadCallbacks> callbacks) {
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
   context_->ui_loop()->PostTask(
       FROM_HERE,
-      base::Bind(
-          &UIServiceLoader::LoadServiceOnUIThread,
-          base::Unretained(this),
-          manager,
-          url,
-          base::Owned(new ScopedMessagePipeHandle(shell_handle.Pass()))));
+      base::Bind(&UIServiceLoader::LoadOnUIThread,
+                 base::Unretained(this),
+                 manager,
+                 url,
+                 base::Owned(
+                     new ScopedMessagePipeHandle(shell_handle.Pass()))));
 }
 
 void UIServiceLoader::OnServiceError(ServiceManager* manager, const GURL& url) {
@@ -64,13 +69,12 @@ void UIServiceLoader::OnServiceError(ServiceManager* manager, const GURL& url) {
                  url));
 }
 
-void UIServiceLoader::LoadServiceOnUIThread(
-    ServiceManager* manager,
-    const GURL& url,
-    ScopedMessagePipeHandle* shell_handle) {
+void UIServiceLoader::LoadOnUIThread(ServiceManager* manager,
+                                     const GURL& url,
+                                     ScopedMessagePipeHandle* shell_handle) {
   if (!ui_loader_)
     ui_loader_ = new UILoader(loader_.get());
-  ui_loader_->LoadService(manager, url, shell_handle->Pass());
+  ui_loader_->Load(manager, url, shell_handle->Pass());
 }
 
 void UIServiceLoader::OnServiceErrorOnUIThread(ServiceManager* manager,
diff --git a/mojo/shell/ui_service_loader_android.h b/mojo/shell/ui_service_loader_android.h
index ebe6df9..8cce709 100644
--- a/mojo/shell/ui_service_loader_android.h
+++ b/mojo/shell/ui_service_loader_android.h
@@ -25,9 +25,9 @@ class UIServiceLoader : public ServiceLoader {
   virtual ~UIServiceLoader();
 
   // ServiceLoader overrides:
-  virtual void LoadService(ServiceManager* manager,
-                           const GURL& url,
-                           ScopedMessagePipeHandle shell_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
   virtual void OnServiceError(ServiceManager* manager,
                               const GURL& url) OVERRIDE;
 
@@ -38,9 +38,9 @@ class UIServiceLoader : public ServiceLoader {
   // to |background_loader_| to do the actual loading.
   // TODO: having this code take a |manager| is fragile (as ServiceManager isn't
   // thread safe).
-  void LoadServiceOnUIThread(ServiceManager* manager,
-                             const GURL& url,
-                             ScopedMessagePipeHandle* shell_handle);
+  void LoadOnUIThread(ServiceManager* manager,
+                      const GURL& url,
+                      ScopedMessagePipeHandle* shell_handle);
   void OnServiceErrorOnUIThread(ServiceManager* manager, const GURL& url);
   void ShutdownOnUIThread();
 
diff --git a/mojo/shell/view_manager_loader.cc b/mojo/shell/view_manager_loader.cc
index bbcca5a..d53accc 100644
--- a/mojo/shell/view_manager_loader.cc
+++ b/mojo/shell/view_manager_loader.cc
@@ -20,10 +20,13 @@ ViewManagerLoader::ViewManagerLoader() {
 ViewManagerLoader::~ViewManagerLoader() {
 }
 
-void ViewManagerLoader::LoadService(
-    ServiceManager* manager,
-    const GURL& url,
-    ScopedMessagePipeHandle shell_handle) {
+void ViewManagerLoader::Load(ServiceManager* manager,
+                             const GURL& url,
+                             scoped_refptr<LoadCallbacks> callbacks) {
+  ScopedMessagePipeHandle shell_handle = callbacks->RegisterApplication();
+  if (!shell_handle.is_valid())
+    return;
+
   // TODO(sky): this needs some sort of authentication as well as making sure
   // we only ever have one active at a time.
   scoped_ptr<ApplicationImpl> app(
diff --git a/mojo/shell/view_manager_loader.h b/mojo/shell/view_manager_loader.h
index bb3a615..6827bac 100644
--- a/mojo/shell/view_manager_loader.h
+++ b/mojo/shell/view_manager_loader.h
@@ -30,10 +30,9 @@ class ViewManagerLoader
 
  private:
   // ServiceLoader overrides:
-  virtual void LoadService(
-      ServiceManager* manager,
-      const GURL& url,
-      ScopedMessagePipeHandle shell_handle) OVERRIDE;
+  virtual void Load(ServiceManager* manager,
+                    const GURL& url,
+                    scoped_refptr<LoadCallbacks> callbacks) OVERRIDE;
   virtual void OnServiceError(ServiceManager* manager,
                               const GURL& url) OVERRIDE;