Add desktop engagement metrics.

chrome/browser/ui/cocoa/browser_window_controller.mm

 // Copyright 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/browser_window_controller.h"
 
 #include <cmath>
 #include <numeric>
 #include <utility>
 
@@ skipping 580 matching lines @@
     [[self window] orderOut:self];
     return NO;
   }
 
   // the tab strip is empty, it's ok to close the window
   return YES;
 }
 
 // Called right after our window became the main window.
 - (void)windowDidBecomeMain:(NSNotification*)notification {
   if (chrome::GetLastActiveBrowser() != browser_.get()) {

[Alexei Svitkine (slow), 2016/07/26 22:00:41]

Do we need to remove this check?

I remember when I tested this locally, if we had this check, then what could
happen is that NotifyBrowserNoLongerActive() could be called when you switched
to a different app and then when you switched back, this check would still
evaluate to them being equal and SetLastActive would never be called.

So I think we *do* need to update this to remove the check. I assume doing so
would make it equivalent to what happens on other platforms, so presumably it
shouldn't cause issues, but you might want to check the history.

... which I just glanced at and seems the if statement was added here:

https://codereview.chromium.org/1105423003

... and later was found to be problematic and modified here:

https://codereview.chromium.org/1370753003

So my reading of the above was the original intention was to limit the
-saveWindowPositionIfNeeded call below but it proved problematic and so we were
left with this artifact if statement that no longer did what it was added for.

So I think removing it here is fine, but please add a comment explaining why we
need to call it unconditionally.

[gayane -on leave until 09-2017, 2016/07/27 21:10:25]

Done.

     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];
 
   NSView* rootView = [[[self window] contentView] superview];
   [rootView cr_recursivelyInvokeBlock:^(id view) {
       if ([view conformsToProtocol:@protocol(ThemedWindowDrawing)])
         [view windowDidChangeActive];
   }];
 
   extensions::ExtensionCommandsGlobalRegistry::Get(browser_->profile())
       ->set_registry_for_active_window(extension_keybinding_registry_.get());
 }
 
 - (void)windowDidResignMain:(NSNotification*)notification {
   NSView* rootView = [[[self window] contentView] superview];
   [rootView cr_recursivelyInvokeBlock:^(id view) {
       if ([view conformsToProtocol:@protocol(ThemedWindowDrawing)])
         [view windowDidChangeActive];
   }];
 
   extensions::ExtensionCommandsGlobalRegistry::Get(browser_->profile())
       ->set_registry_for_active_window(nullptr);
+
+  BrowserList::NotifyBrowserNoLongerActive(browser_.get());
 }
 
 // Called when we have been minimized.
 - (void)windowDidMiniaturize:(NSNotification *)notification {
   [self saveWindowPositionIfNeeded];
 }
 
 // Called when we have been unminimized.
 - (void)windowDidDeminiaturize:(NSNotification *)notification {
   // Make sure the window's show_state (which is now ui::SHOW_STATE_NORMAL)
@@ skipping 1416 matching lines @@
 
 - (NSRect)savedRegularWindowFrame {
   return savedRegularWindowFrame_;
 }
 
 - (BOOL)isFullscreenTransitionInProgress {
   return enteringAppKitFullscreen_ || exitingAppKitFullscreen_;
 }
 
 @end  // @implementation BrowserWindowController(WindowType)