[Blimp] Creates engine tab class to handle tab related operations.

blimp/engine/session/tab.h

Index: blimp/engine/session/tab.h
diff --git a/blimp/engine/session/tab.h b/blimp/engine/session/tab.h
new file mode 100644
index 0000000000000000000000000000000000000000..1e9d652440f5be9fcfba7430b50066225477e54a
--- /dev/null
+++ b/blimp/engine/session/tab.h
@@ -0,0 +1,74 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.

[Kevin M, 2016/06/07 22:43:43]

Unit tests? :)

[haibinlu, 2016/06/08 17:57:22]

per offline discussion, we should add some browser test cases for tab controls
instead.  

[maniscalco, 2016/06/08 19:59:39]

Not that I necessarily disagree, but could you elaborate on why we're not adding
unit test for this new class?

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BLIMP_ENGINE_SESSION_TAB_BLIMP_H_
+#define BLIMP_ENGINE_SESSION_TAB_BLIMP_H_
+
+#include "base/macros.h"
+#include "content/public/browser/invalidate_type.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "blimp/engine/session/page_load_tracker.h"
+
+namespace content {
+class RenderViewHost;
+class WebContents;
+}
+
+namespace blimp {
+class BlimpMessageProcessor;
+
+namespace engine {
+class EngineRenderWidgetFeature;
+
+// Owns WebContents, handles operations in the tab, and has one-to-one mapping
+// to a client tab.
+class Tab : public content::WebContentsObserver, public PageLoadTrackerClient {
+ public:
+  // Caller ensures |render_widget_feature| and |navigation_message_sender|
+  // outlives this object.
+  // |web_contents|: the WebContents this tab owns.
+  // |tab_id|: the ID of this tab.
+  // |render_widget_feature|: render widget feature.
+  // |navigation_message_sender|: for sending navigation messages to client.
+  Tab(std::unique_ptr<content::WebContents> web_contents,
+      const int tab_id,
+      EngineRenderWidgetFeature* render_widget_feature,
+      BlimpMessageProcessor* navigation_message_sender);
+  ~Tab() override;
+
+  content::WebContents* web_contents() { return web_contents_.get(); }
+  int tab_id() const { return tab_id_; }
+
+  void Resize(float device_pixel_ratio, const gfx::Size& size_in_dips);
+  void LoadUrl(const GURL& url);
+  void GoBack();
+  void GoForward();
+  void Reload();
+  void NavigationStateChanged(content::InvalidateTypes changed_flags);
+
+  // PageLoadTrackerClient implementation.
+  void SendPageLoadStatusUpdate(PageLoadStatus load_status) override;
+
+ private:
+  // content::WebContentsObserver implementation.
+  void RenderViewCreated(content::RenderViewHost* render_view_host) override;
+  void RenderViewHostChanged(content::RenderViewHost* old_host,
+                             content::RenderViewHost* new_host) override;
+  void RenderViewDeleted(content::RenderViewHost* render_view_host) override;
+
+  std::unique_ptr<content::WebContents> web_contents_;
+  const int tab_id_;
+  EngineRenderWidgetFeature* render_widget_feature_;
+  BlimpMessageProcessor* navigation_message_sender_;
+
+  // Tracks the page load status for a tab.
+  std::unique_ptr<PageLoadTracker> page_load_tracker_;
+
+  DISALLOW_COPY_AND_ASSIGN(Tab);
+};
+
+}  // namespace engine
+}  // namespace blimp
+
+#endif  // BLIMP_ENGINE_SESSION_TAB_BLIMP_H_