Tabs being screen-captured will fullscreen within their tab contents area.

chrome/browser/ui/fullscreen/fullscreen_controller_interactive_browsertest.cc

 // 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.
 
 #include "build/build_config.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/fullscreen.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_commands.h"
@@ skipping 630 matching lines @@
 
   // Request to lock the mouse and enter fullscreen.
   FullscreenNotificationObserver fullscreen_observer;
   ASSERT_TRUE(ui_test_utils::SendKeyPressAndWait(
       browser(), ui::VKEY_B, false, true, false, false,
       chrome::NOTIFICATION_MOUSE_LOCK_CHANGED,
       content::NotificationService::AllSources()));
   fullscreen_observer.Wait();
 
   // Confirm they are enabled and there is no prompt.
-  ASSERT_TRUE(IsFullscreenBubbleDisplayed());
+  ASSERT_FALSE(IsFullscreenBubbleDisplayed());

[miu, 2014/02/12 08:25:20]

This test, that I originally authored, was broken in a previous CL.  By me. 
Because I forgot to manually run these tests for
https://codereview.chromium.org/26803002.  I hang my head in shame.

BTW--The correct behavior *is* for the bubble not to be displayed.  This is the
test for Flash widgets that are Fullscreened-Within-Tab.  Flash is responsible
for displaying the "Press Esc to exit fullscreen" message, not the bubble.

   ASSERT_FALSE(IsFullscreenPermissionRequested());
   ASSERT_FALSE(IsMouseLockPermissionRequested());
   ASSERT_TRUE(IsMouseLocked());
   ASSERT_TRUE(IsFullscreenForTabOrPending());
 }
 
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS) && defined(USE_AURA)
 // TODO(erg): linux_aura bringup: http://crbug.com/163931
 #define MAYBE_MouseLockSilentAfterTargetUnlock \
   DISABLED_MouseLockSilentAfterTargetUnlock
@@ skipping 262 matching lines @@
 
   GURL url = test_server()->GetURL("simple.html");
   AddTabAtIndex(0, url, PAGE_TRANSITION_TYPED);
 
   // Validate that going fullscreen for a URL defaults to asking permision.
   ASSERT_FALSE(IsFullscreenPermissionRequested());
   ASSERT_NO_FATAL_FAILURE(ToggleTabFullscreenNoRetries(true));
   ASSERT_TRUE(IsFullscreenPermissionRequested());
   ASSERT_NO_FATAL_FAILURE(ToggleTabFullscreenNoRetries(false));
 }