Make tab audible and muted states and cause available for an extension API

chrome/browser/ui/cocoa/tabs/tab_strip_controller.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/tabs/tab_strip_controller.h"
 
 #import <QuartzCore/QuartzCore.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 813 matching lines @@
   }
 }
 
 // Called when the user clicks the tab audio indicator to mute the tab.
 - (void)toggleMute:(id)sender {
   DCHECK([sender isKindOfClass:[TabView class]]);
   NSInteger index = [self modelIndexForTabView:sender];
   if (!tabStripModel_->ContainsIndex(index))
     return;
   WebContents* contents = tabStripModel_->GetWebContentsAt(index);
-  chrome::SetTabAudioMuted(contents, !chrome::IsTabAudioMuted(contents));
+  chrome::SetTabAudioMuted(contents, !chrome::IsTabAudioMuted(contents), "user");

[miu, 2014/12/05 23:46:48]

Instead of passing "user" as a cause, it's best to have this string constant
declared/defined in one place and then used by all the call points.

Suggestion: Add a static constant to tab_utils.cc:

  const char kUserMuteToggleCause[] = "user";

[Jared Sohn, 2014/12/07 22:39:45]

I also need access to this constant from
chrome/browser/ui/views/tabs/browser_tab_strip_controller.cc.  

Would it be better to redundantly declare the same constant in that file or
define it once in a shared header file?  Since both classes make use of
tab_utils.h, I have considered moving the constant to there (and then placing it
within the chrome namespace since that is what the function that uses it uses.)

Is this okay, or is there a preference for not putting string constants in
header files (perhaps because it will get instantiated by any file that includes
it, even if it doesn't use it?  Although, since it is static it will only get
instantiated once, so its very small negative effect would be allocating space
when modules that don't call the function but use the header file get built.)

[miu, 2014/12/09 01:56:24]

The way you did it is the preferred way, with one minor thing.  See next comment
for clarification...

 }
 
 // Called when the user closes a tab. Asks the model to close the tab. |sender|
 // is the TabView that is potentially going away.
 - (void)closeTab:(id)sender {
   DCHECK([sender isKindOfClass:[TabView class]]);
 
   // Cancel any pending tab transition.
   hoverTabSelector_->CancelTabTransition();
 
@@ skipping 1469 matching lines @@
   // up the hierarchy to the devtools container view to avoid that. Note that
   // the devtools view is always in the hierarchy even if it is not open or it
   // is detached.
   NSView* devtools_view = [[[view superview] superview] superview];
   if (devtools_view) {
     return [devtools_view convertRect:[devtools_view bounds] toView:nil];
   } else {
     return [view convertRect:[view bounds] toView:nil];
   }
 }