Stretching NativeViewHost, and misc tab capture fixes.

chrome/browser/ui/cocoa/tab_contents/tab_contents_controller.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_UI_COCOA_TAB_CONTENTS_TAB_CONTENTS_CONTROLLER_H_
 #define CHROME_BROWSER_UI_COCOA_TAB_CONTENTS_TAB_CONTENTS_CONTROLLER_H_
 
 #include <Cocoa/Cocoa.h>
 
 #include <memory>
 
 class FullscreenObserver;
 
 namespace content {
 class WebContents;
 }
 
 // A class that controls the WebContents view. It internally creates a container
 // view (the NSView accessed by calling |-view|) which manages the layout and
 // display of the WebContents view.
 //
 // Client code that inserts [controller view] into the view hierarchy needs to
 // call -ensureContentsVisibleInSuperview:(NSView*)superview to match the
 // container to the [superview bounds] and avoid multiple resize messages being
 // sent to the renderer, which triggers redundant and costly layouts.
 //
 // AutoEmbedFullscreen mode: When enabled, TabContentsController will observe
 // for WebContents fullscreen changes and automatically swap the normal
 // WebContents view with the fullscreen view (if different). In addition, if a
-// WebContents is being screen-captured, the view will be centered within the
-// container view, sized to the aspect ratio of the capture video resolution,
-// and scaling will be avoided whenever possible.
+// WebContents is being screen-captured, the WebContentsView will be centered
+// within the container view and sized to the aspect ratio of the capture video
+// resolution; also, the WebContentsView will be sized so that the page is
+// rendered at the capture video resolution. This means the container view can
+// have a different size than the WebContentsView, and the tab content may
+// appear scaled within the browser window on the local screen. The reason for
+// doing all this is to improve quality and performance: For example, pages that
+// stream video content will dynamically adapt their video playback resolution
+// based on their rendering size; and so this should ideally match the tab
+// capture size.
 @interface TabContentsController : NSViewController {
  @private
    content::WebContents* contents_;  // weak
    // When |fullscreenObserver_| is not-NULL, TabContentsController monitors for
    // and auto-embeds fullscreen widgets as a subview.
    std::unique_ptr<FullscreenObserver> fullscreenObserver_;
    // Set to true while TabContentsController is embedding a fullscreen widget
    // view as a subview instead of the normal WebContentsView render view.
    // Note: This will be false in the case of non-Flash fullscreen.
    BOOL isEmbeddingFullscreenWidget_;
@@ skipping 41 matching lines @@
 // an entirely new tab contents object.
 - (void)tabDidChange:(content::WebContents*)updatedContents;
 
 // Called to switch the container's subview to the WebContents-owned fullscreen
 // widget or back to WebContentsView's widget.
 - (void)toggleFullscreenWidget:(BOOL)enterFullscreen;
 
 @end
 
 #endif  // CHROME_BROWSER_UI_COCOA_TAB_CONTENTS_TAB_CONTENTS_CONTROLLER_H_