Add desktop engagement metrics.

chrome/browser/ui/cocoa/browser_window_controller.mm

Index: chrome/browser/ui/cocoa/browser_window_controller.mm
diff --git a/chrome/browser/ui/cocoa/browser_window_controller.mm b/chrome/browser/ui/cocoa/browser_window_controller.mm
index 0f9b7296a03c4420f1671ce6bcc379ce44020d32..f25a5c79f31576a63a6c6a111c209cb317c02608 100644
--- a/chrome/browser/ui/cocoa/browser_window_controller.mm
+++ b/chrome/browser/ui/cocoa/browser_window_controller.mm
@@ -598,9 +598,10 @@ bool IsTabDetachingInFullscreenEnabled() {
 
 // Called right after our window became the main window.
 - (void)windowDidBecomeMain:(NSNotification*)notification {
-  if (chrome::GetLastActiveBrowser() != browser_.get()) {
-    BrowserList::SetLastActive(browser_.get());
-  }
+  // Set this window as active even if the previously active windows was the

[Lei Zhang, 2016/08/01 17:29:02]

Funny enough, before https://codereview.chromium.org/1105423003 the code was
written like this, but without any of the comments here and at line 605.

[gayane -on leave until 09-2017, 2016/08/02 17:13:44]

Yes, there is also this CL https://codereview.chromium.org/1370753003 following
that one which I think left the check for no reason anymore and in our case we
needed to remove the check so that when browser loses the focus the notification
is always sent.

+  // same one. This is needed for tracking visibility changes of a browser.
+  BrowserList::SetLastActive(browser_.get());
+
   // Always saveWindowPositionIfNeeded when becoming main, not just
   // when |browser_| is not the last active browser. See crbug.com/536280 .
   [self saveWindowPositionIfNeeded];
@@ -624,6 +625,8 @@ bool IsTabDetachingInFullscreenEnabled() {
 
   extensions::ExtensionCommandsGlobalRegistry::Get(browser_->profile())
       ->set_registry_for_active_window(nullptr);
+
+  BrowserList::NotifyBrowserNoLongerActive(browser_.get());
 }
 
 // Called when we have been minimized.