[Android] Upstream ChromeBrowserProvider, the Android port ContentProvider implementation.

chrome/browser/android/provider/blocking_ui_thread_async_request.h

+// Copyright (c) 2012 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.
+
+#ifndef CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_
+#define CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/synchronization/waitable_event.h"
+#include "chrome/browser/android/provider/run_on_ui_thread_blocking.h"
+#include "content/public/browser/browser_thread.h"
+
+// Allows making async requests and blocking the current thread until the
+// response arrives. The request is performed in the UI thread.
+// Users of this class MUST call RequestCompleted when receiving the response.
+// Cannot be called directly from the UI thread.
+class BlockingUIThreadAsyncRequest {
+ public:
+  BlockingUIThreadAsyncRequest();
+
+  // Runs an asynchronous request, blocking the invoking thread until a response
+  // is received. Class users MUST call RequestCompleted when this happens.
+  // Make sure that the response is also delivered to the UI thread.
+  // The request argument can be defined using base::Bind.
+  template <typename Signature>
+  void RunAsyncRequestOnUIThreadBlocking(base::Callback<Signature> request) {
+    DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+
+    // Make the request in the UI thread.
+    request_completed_.Reset();
+    RunOnUIThreadBlocking::Run(
+        base::Bind(
+            &BlockingUIThreadAsyncRequest::RunRequestOnUIThread<Signature>,
+            request));
+
+    // Wait until the request callback invokes Finished.
+    request_completed_.Wait();
+  }
+
+  // Notifies about a finished request.
+  void RequestCompleted();
+
+ private:
+  template <typename Signature>
+  static void RunRequestOnUIThread(base::Callback<Signature> request) {
+    request.Run();
+  }
+
+  base::WaitableEvent request_completed_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlockingUIThreadAsyncRequest);
+};
+
+#endif  // CHROME_BROWSER_ANDROID_PROVIDER_BLOCKING_UI_THREAD_ASYNC_REQUEST_H_