Add a full Blimp integration test.

blimp/engine/browser_tests/waitable_content_pump.h

Index: blimp/engine/browser_tests/waitable_content_pump.h
diff --git a/blimp/engine/browser_tests/waitable_content_pump.h b/blimp/engine/browser_tests/waitable_content_pump.h
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+++ b/blimp/engine/browser_tests/waitable_content_pump.h
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+// Copyright 2016 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 BLIMP_ENGINE_BROWSER_TESTS_WAITABLE_CONTENT_PUMP_H_
+#define BLIMP_ENGINE_BROWSER_TESTS_WAITABLE_CONTENT_PUMP_H_
+
+#include "base/macros.h"
+#include "base/synchronization/waitable_event.h"
+
+namespace blimp {
+
+// A helper class to suspend execution on the current stack and still allow all
+// content message loops to run until a WaitableEvent is signaled.  This
+// currently only pumps the UI, IO, and FILE threads.  The typical use case
+// would look like:
+//
+// WaitableContentPump waiter;
+// GiveEventToSomeoneToEventuallySignal(waiter.event());
+// waiter.Wait();

[Khushal, 2016/09/13 23:47:10]

Awesome comment. Thanks!

[David Trainor- moved to gerrit, 2016/09/14 00:31:09]

Acknowledged.

+class WaitableContentPump {
+ public:
+  WaitableContentPump();
+  virtual ~WaitableContentPump();
+
+  // Helper methods to use the WaitableContentPump without needing to build a
+  // WaitableEvent.
+  base::WaitableEvent* event() { return &event_; }
+  void Wait();
+
+  // Pumps content message loops until |event| is signaled.  This will reset
+  // |event| afterwards.
+  void WaitFor(base::WaitableEvent* event);

[Khushal, 2016/09/13 23:47:10]

If this is meant to be just a helper method for others to use, make it static?

[David Trainor- moved to gerrit, 2016/09/14 00:31:09]

Done.

+
+ private:
+  base::WaitableEvent event_;
+
+  DISALLOW_COPY_AND_ASSIGN(WaitableContentPump);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_ENGINE_BROWSER_TESTS_WAITABLE_CONTENT_PUMP_H_