[mac][views] Notify web_contents focused.

content/browser/web_contents/web_contents_view_mac.mm

Index: content/browser/web_contents/web_contents_view_mac.mm
diff --git a/content/browser/web_contents/web_contents_view_mac.mm b/content/browser/web_contents/web_contents_view_mac.mm
index b87c8b96365db41b59054e359dbcec885d3f729c..80a5f27e8bae3a7feec667e5fd908274abcbbbf4 100644
--- a/content/browser/web_contents/web_contents_view_mac.mm
+++ b/content/browser/web_contents/web_contents_view_mac.mm
@@ -183,6 +183,7 @@ void WebContentsViewMac::Focus() {
   if (![window isVisible])
     return;
   [window makeKeyAndOrderFront:nil];
+  web_contents_->NotifyWebContentsFocused();

[tapted, 2016/05/27 11:50:37]

I don't think this is the right place for it. Aura does it in `GotFocus` but
there's a comment there for Mac:

void WebContentsViewMac::GotFocus() {
  // This is only used in the views FocusManager stuff but it bleeds through
  // all subclasses. http://crbug.com/21875
}

So yup - nothing on Mac calls NotifyWebContentsFocused() (except embedded
fullscreen widgets?). But that's fine because there's exactly one observer:
views::WebView, which only exists in MacViewsBrowser.

So.. IMO it's OK just to use the same GotFocus() implementation as
WebContentsViewAura to hook this up. I don't think there's a significant
downside for the Cocoa browser. But avi@ is the person to ask :)

I guess you could set BUG+=21875 for this, since I guess that would be fixed by
this too.

[Avi (use Gerrit), 2016/05/27 15:42:36]

Agreed.

I'm trusting in the Views people that plumbing GotFocus into WebContents was the
correct decision, but if it was, then let's mirror that behavior here. Trying to
keep things being done in the same way on all the platforms is very important.

[yamaxim, 2016/05/30 12:32:38]

I wrap it with GotFocus, if you can say a better place for call GotFocus, I
would like to move it.

 }
 
 void WebContentsViewMac::SetInitialFocus() {