Adding tools menu responsiveness metric.

ios/chrome/browser/ui/browser_view_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 "ios/chrome/browser/ui/browser_view_controller.h"
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <MobileCoreServices/MobileCoreServices.h>
 #import <PassKit/PassKit.h>
 #import <Photos/Photos.h>
@@ skipping 3366 matching lines @@
     // doing, and what the PM want, but it doesn't make it right.
   }
 }
 
 #pragma mark - Showing popups
 
 - (void)showToolsMenuPopup {
   DCHECK(_browserState);
   DCHECK(self.visible || self.dismissingModal);
 
+  // Record the responsiveness of this show menu operation.
+  NSTimeInterval startTime = [NSDate timeIntervalSinceReferenceDate];

[rohitrao (ping after 24h), 2017/05/18 01:16:25]

Another option would be to add this startTime to ToolsMenuConfiguration and read
it from there when the animation completes.  It's not really menu configuration
data, but it would simplify the logic a bit and avoid adding a new notification.
 It's also a bit safer if we ever fail to run the toolsmenu animation for some
reason, since we wouldn't have a block that could leak.

Thoughts?  Which do you prefer?

[PL, 2017/05/18 23:36:34]

Done! This is a smart idea... the configuration isn't stored anywhere at
present, but I can just store the value from the configuration in the view
controller and use it.

I do think this will result in a smaller amount of code... although it does
introduce two instance variables purely for the use of metrics (whereas before I
had none, if you consider the 'didShow' notification could be used for something
non-metric related).

+  __block id<NSObject> oneTimeObserver = [[NSNotificationCenter defaultCenter]
+      addObserverForName:kMenuDidShowNotification
+                  object:nil
+                   queue:nil
+              usingBlock:^(NSNotification* _Nonnull note) {
+                UMA_HISTOGRAM_TIMES(
+                    "UI.Performance.ShowToolsMenuResponsiveness",
+                    base::TimeDelta::FromSecondsD(
+                        [NSDate timeIntervalSinceReferenceDate] - startTime));
+                [[NSNotificationCenter defaultCenter]
+                    removeObserver:oneTimeObserver];
+                oneTimeObserver = nil;
+              }];
+
   // Dismiss the omnibox (if open).
   [_toolbarController cancelOmniboxEdit];
   // Dismiss the soft keyboard (if open).
   [[_model currentTab].webController dismissKeyboard];
   // Dismiss Find in Page focus.
   [self updateFindBar:NO shouldFocus:NO];
 
   ToolsMenuConfiguration* configuration =
       [[ToolsMenuConfiguration alloc] initWithDisplayView:[self view]];
   if ([_model count] == 0)
@@ skipping 1772 matching lines @@
 
 - (UIView*)voiceSearchButton {
   return _voiceSearchButton;
 }
 
 - (id<LogoAnimationControllerOwner>)logoAnimationControllerOwner {
   return [self currentLogoAnimationControllerOwner];
 }
 
 @end