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

chrome/browser/android/provider/run_on_ui_thread_blocking.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_RUN_ON_UI_THREAD_BLOCKING_H_
+#define CHROME_BROWSER_ANDROID_PROVIDER_RUN_ON_UI_THREAD_BLOCKING_H_
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/synchronization/waitable_event.h"
+#include "content/public/browser/browser_thread.h"
+
+// Runs code synchronously on the UI thread. Should never be called directly
+// from the UI thread. To be used only within the provider classes.
+class RunOnUIThreadBlocking {
+ public:
+  // Runs the provided runnable in the UI thread synchronously.
+  // The runnable argument can be defined using base::Bind.
+  template <typename Signature>
+  static void Run(base::Callback<Signature> runnable) {
+    DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+    base::WaitableEvent finished(false, false);
+    content::BrowserThread::PostTask(content::BrowserThread::UI, FROM_HERE,
+          base::Bind(&RunOnUIThreadBlocking::RunOnUIThread<Signature>,
+                     runnable, &finished));
+    finished.Wait();
+  }
+
+ private:
+  template <typename Signature>
+  static void RunOnUIThread(base::Callback<Signature> runnable,
+                            base::WaitableEvent* finished) {
+    DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+    runnable.Run();
+    finished->Signal();
+  }
+};
+
+#endif  // CHROME_BROWSER_ANDROID_PROVIDER_RUN_ON_UI_THREAD_BLOCKING_H_