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

chrome/browser/ui/fullscreen/fullscreen_controller.h

Index: chrome/browser/ui/fullscreen/fullscreen_controller.h
diff --git a/chrome/browser/ui/fullscreen/fullscreen_controller.h b/chrome/browser/ui/fullscreen/fullscreen_controller.h
index 6a5aa4b517bc6ab06f0a79d1e676c35cca2d5ead..0ec48b9aa356b5a20959da1030ba74499bd25394 100644
--- a/chrome/browser/ui/fullscreen/fullscreen_controller.h
+++ b/chrome/browser/ui/fullscreen/fullscreen_controller.h
@@ -5,6 +5,8 @@
 #ifndef CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_
 #define CHROME_BROWSER_UI_FULLSCREEN_FULLSCREEN_CONTROLLER_H_
 
+#include <vector>
+
 #include "base/basictypes.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/ui/fullscreen/fullscreen_exit_bubble_type.h"
@@ -34,6 +36,14 @@ class WebContents;
 // For Flash, FullscreenController will auto-accept all permission requests for
 // fullscreen and/or mouse lock, since the assumption is that the plugin handles
 // this for us.
+//
+// Special behavior for screen-captured tabs: When embedded fullscreen widgets

[scheib, 2014/02/12 01:41:16]

Consider anchoring/naming this note with e.g. 
"""
EmbeddedFullscreen Note: 
Special behavior ...
"""

And then referencing elsewhere with "See 'EmbeddedFullscreen Note'"

[miu, 2014/02/12 08:25:19]

Done.

+// are enabled and the renderer toggles into fullscreen mode, the browser window
+// will not expand to enter fullscreen.  This allows the user to retain control
+// of their desktop to work in other browser tabs or applications while the
+// fullscreen view is displayed on a remote screen.  FullscreenController will
+// track which WebContentses have renderers in fullscreen mode, and use an
+// alternate set of heuristics to manage them.
 
 // This class implements fullscreen and mouselock behaviour.
 class FullscreenController : public content::NotificationObserver {
@@ -54,6 +64,13 @@ class FullscreenController : public content::NotificationObserver {
   // Returns true if fullscreen has been caused by a tab.
   // The window may still be transitioning, and window_->IsFullscreen()
   // may still return false.
+  //
+  // NOTE: The zero-argument version returns true iff a fullscreen tab will

[scheib, 2014/02/12 01:41:16]

For clarity (presuming I have it right): "iff a fullscreen tab and its browser
window is(or will be) fullscreen."

[miu, 2014/02/12 08:25:19]

Done.

+  // result in the browser window expanding to fill the screen.  On the other
+  // hand, the one-argument version will return true while the renderer is/will
+  // be in fullscreen mode, but not necessarily the browser window.  The latter
+  // case accounts for the special behavior employed during screen capture of a

[scheib, 2014/02/12 01:41:16]

And then reference "See 'EmbeddedFullscreen Note'"

[miu, 2014/02/12 08:25:19]

Done.

+  // WebContents where the fullscreen view remains within the browser tab.
   bool IsFullscreenForTabOrPending() const;

[scheib, 2014/02/12 01:41:16]

Consider renaming the method to differentiate the meaning between the two,
overloading is getting dicey here.

[miu, 2014/02/12 08:25:19]

Agreed.  There are quite a few callers of it, so I'd prefer to follow this up in
a separate clean-up CL.  SGTY?

[scheib, 2014/02/12 18:01:36]

Yes.

   bool IsFullscreenForTabOrPending(
       const content::WebContents* web_contents) const;
@@ -98,6 +115,9 @@ class FullscreenController : public content::NotificationObserver {
   // Called by Browser::TabDeactivated.
   void OnTabDeactivated(content::WebContents* web_contents);
 
+  // Called by Browser::ActiveTabChanged.
+  void OnTabDetachedFromView(content::WebContents* web_contents);
+
   // Called by Browser::TabClosingAt.
   void OnTabClosing(content::WebContents* web_contents);
 
@@ -173,6 +193,16 @@ class FullscreenController : public content::NotificationObserver {
 
   bool IsPrivilegedFullscreenForTab() const;
   void SetPrivilegedFullscreenForTesting(bool is_privileged);
+  // Returns true if embedded fullscreen features have been enabled for the
+  // |browser_|.

[scheib, 2014/02/12 01:41:16]

And then reference "See 'EmbeddedFullscreen Note'" for these.

[miu, 2014/02/12 08:25:19]

Done.

+  bool IsEmbeddedFullscreenEnabled() const;

[scheib, 2014/02/12 01:41:16]

Use a consistent terminology, always 'EmbeddedFullscreen' or
'FullscreenWithinTab', or 'CapturedFullscreen' or ScreenCapture'... but pick
one.

Also, IsEmbeddedFullscreenEnabled and IsCapturedFullscreenTab are similar, and a
tad confusing.

Here's a proposal for these methods in order:
IsEmbeddedFullscreenPossible
MaybeToggleEmbeddedFullscreen
IsEmbeddedFullscreen

[miu, 2014/02/12 08:25:19]

I see your point, and agree the naming was confusing.  Please take a look at how
I rewrote the 'FullscreenWithinTab Note' at the top of this file, since it
points out how there are two related pieces of functionality at play here
(http://crbug.com/290403 versus http://crbug.com/256870).  Both involve showing
fullscreen widgets within the tab contents area.  The special-case (introduced
by this CL) is when a tab is being screen-captured: We do not fullscreen the
browser window.

I've reworked the naming of the methods (and terminology in comments) to be
consistent and also clarify differences.  I decided to stop using the "embedded
fullscreen" terminology altogether since it is overused throughout Chromium code
and could be easily confused with unrelated NPAPI special-case foo in
src/content.

[scheib, 2014/02/12 18:01:36]

Thanks - I think it's clearer now - though still subtle that
'FullscreenWithinTab' is a super set of 'FullscreenForCapturedTab'. 

+  // Returns true if |web_contents| is/was being screen-captured and was
+  // toggled into/out of fullscreen-within-tab mode.
+  bool MaybeToggleAsFullscreenWithinTab(content::WebContents* web_contents,
+                                        bool enter_fullscreen);
+  // Returns true if |web_contents| has its fullscreen view embedded within a
+  // browser tab and is being screen captured.
+  bool IsCapturedFullscreenTab(const content::WebContents* web_contents) const;
   void UnlockMouse();
 
   Browser* const browser_;
@@ -217,6 +247,12 @@ class FullscreenController : public content::NotificationObserver {
   // WindowFullscreenStateChanged do so.
   bool reentrant_window_state_change_call_check_;
 
+  // A WebContents pointer is in this set if it entered fullscreen mode during
+  // screen capture.  In other words, this tracks those WebContentses that are
+  // in fullscreen mode, but the browser window is not.  Note: Behavior only
+  // applies when IsEmbeddedFullscreenEnabled() returns true.
+  std::vector<const content::WebContents*> captured_tabs_;
+
   // Used in testing to confirm proper behavior for specific, privileged
   // fullscreen cases.
   bool is_privileged_fullscreen_for_testing_;