headless: Initial headless embedder API implementation

headless/public/headless_web_contents.h

+// 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.
+
+#ifndef HEADLESS_PUBLIC_HEADLESS_WEB_CONTENTS_H_
+#define HEADLESS_PUBLIC_HEADLESS_WEB_CONTENTS_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "headless/public/headless_export.h"
+#include "url/gurl.h"
+
+namespace headless {
+
+// Class representing contents of a browser tab. Should be accessed from browser
+// main thread.
+class HEADLESS_EXPORT HeadlessWebContents {
+ public:
+  virtual ~HeadlessWebContents() {}
+
+  // TODO(skyostil): Replace this with an equivalent client API.
+  class Observer {
+   public:
+    // Will be called on browser thread.
+    virtual void DocumentOnLoadCompletedInMainFrame() = 0;
+
+   protected:
+    // Use this constructor when the observer's lifetime matches that of the
+    // HeadlessWebContents.
+    explicit Observer(HeadlessWebContents* web_contents);

[Ryan Sleevi, 2016/02/22 22:01:22]

This seems like it violates the SingleResponsibilityPrinciple, and tightly links
the two objects, beyond what may be necessary. Is this CTOR needed?

(Put differently, does this need to be a concrete base class, or can it be a
pure virtual?)

[Sami, 2016/02/23 20:19:08]

This was modeled after WebContentsObserver which has a similarly split
personality. I'm not crazy about that approach either, so I've just made this
pure virtual instead.

+
+    // This constructor creates a detached observer. Use Observe() to attach it
+    // to a HeadlessWebContents instance.
+    Observer();
+    virtual ~Observer();
+
+    void Observe(HeadlessWebContents* web_contents);
+
+   private:
+    class ObserverImpl;
+    scoped_ptr<ObserverImpl> observer_impl_;
+
+    DISALLOW_COPY_AND_ASSIGN(Observer);
+  };
+
+  // TODO(skyostil): Replace this with an equivalent client API.
+  virtual void OpenURL(const GURL& url) = 0;
+
+ private:
+  friend class HeadlessWebContentsImpl;
+  HeadlessWebContents() {}
+
+  DISALLOW_COPY_AND_ASSIGN(HeadlessWebContents);
+};
+
+}  // namespace headless
+
+#endif  // HEADLESS_PUBLIC_HEADLESS_WEB_CONTENTS_H_