Add PreviewsInfoBarTabHelper

chrome/browser/previews/previews_infobar_tab_helper.h

+// 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 CHROME_BROWSER_PREVIEWS_PREVIEWS_INFOBAR_TAB_HELPER_H_
+#define CHROME_BROWSER_PREVIEWS_PREVIEWS_INFOBAR_TAB_HELPER_H_
+
+#include "base/macros.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+class GURL;
+
+namespace content {
+class RenderFrameHost;
+}
+
+// Per-tab class to help manage the previews infobar. Handles showing the
+// infobar for LitePages when the main frame response came back with a

[bengr, 2016/08/31 23:27:04]

This seems like an implementation detail. How about:

Handles showing the infobar when the main frame response indicates a Lite Page.

[megjablon, 2016/09/08 00:25:15]

Done.

+// Chrome-Proxy reponse header that has the "q=preview" directive.
+class PreviewsInfoBarTabHelper

[bengr, 2016/08/31 23:27:04]

This class should have tests.

[megjablon, 2016/09/08 00:25:15]

Tests are added in https://chromiumcodereview.appspot.com/2266653002/

Haven't sent this cl out for review because I didn't want to spam a ton of cls
at once. I wanted to get the most important cls that would affect how the others
are implemented reviewed first. 

+    : public content::WebContentsObserver,
+      public content::WebContentsUserData<PreviewsInfoBarTabHelper> {
+ public:
+  ~PreviewsInfoBarTabHelper() override;
+
+  // Indicates whether the InfoBar for Data Reduction Proxy preview has been

[bengr, 2016/08/31 23:27:04]

for -> for the

Also, what is a DRP preview and how is it different from a preview shown for a
Lite Page?

[megjablon, 2016/09/08 00:25:15]

Removed. This should just be for all previews, not only drp dependent ones.

+  // shown for the page.
+  bool DisplayedPreviewInfoBar() const;

[bengr, 2016/08/31 23:27:04]

These are just simple getters and setters so they can be inlined, use underscore
naming, and not be commented:

bool displayed_preview_infobar() const {
  return displayed_preview_infobar_;
}

void set_displayed_preview_infobar(bool displayed) {
  displayed_preview_infobar_ = displayed;
}

[megjablon, 2016/09/08 00:25:15]

Done.

+  void SetDisplayedPreviewInfoBar(bool displayed);
+
+ private:
+  friend class content::WebContentsUserData<PreviewsInfoBarTabHelper>;
+
+  explicit PreviewsInfoBarTabHelper(content::WebContents* web_contents);
+
+  // Overridden from content::WebContentsObserver:
+  void DidStartProvisionalLoadForFrame(
+      content::RenderFrameHost* render_frame_host,
+      const GURL& validated_url,
+      bool is_error_page,
+      bool is_iframe_srcdoc) override;
+  void DidFinishNavigation(
+      content::NavigationHandle* navigation_handle) override;
+
+  // True if the InfoBar for Data Reduction Proxy preview has been shown for

[bengr, 2016/08/31 23:27:04]

for -> for the

[megjablon, 2016/09/08 00:25:15]

Done.

+  // the page.
+  bool displayed_preview_infobar_;
+
+  DISALLOW_COPY_AND_ASSIGN(PreviewsInfoBarTabHelper);
+};
+
+#endif  // CHROME_BROWSER_PREVIEWS_PREVIEWS_INFOBAR_TAB_HELPER_H_