[ios] Remove expired metric IOS.SharePageLatency

This was originally created in Nov 2017 in this CL:
https://chromium-review.googlesource.com/760036

This metric is no longer being used and has already expired
since M77.

Per go/histogram-expiry-guidelines:
"If the histogram is not in use now,
but might be useful in the far future, remove it."

Change-Id: Ic8e899f850f8cea0774500eabe43e87f0aaf87d0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2581003
Auto-Submit: edchin <edchin@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#835194}

ios/chrome/browser/ui/activity_services/activity_service_coordinator.mm

@@ -4,8 +4,6 @@
 
 #import "ios/chrome/browser/ui/activity_services/activity_service_coordinator.h"
 
-#include "base/metrics/histogram_macros.h"
-#include "base/time/time.h"
 #include "components/bookmarks/browser/bookmark_model.h"
 #include "ios/chrome/browser/bookmarks/bookmark_model_factory.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
@@ -33,20 +31,10 @@
 #error "This file requires ARC support."
 #endif
 
-namespace {
-// The histogram key to report the latency between the start of the Share Page
-// operation and when the UI is ready to be presented.
-const char kSharePageLatencyHistogram[] = "IOS.SharePageLatency";
-
-}  // namespace
-
 @interface ActivityServiceCoordinator ()
 
 @property(nonatomic, weak) id<BrowserCommands, FindInPageCommands> handler;
 
-// The time when the Share Page operation started.
-@property(nonatomic, assign) base::TimeTicks sharePageStartTime;
-
 @property(nonatomic, strong) ActivityServiceMediator* mediator;
 
 @property(nonatomic, strong) UIActivityViewController* viewController;
@@ -155,8 +143,6 @@ const char kSharePageLatencyHistogram[] = "IOS.SharePageLatency";
 // Fetches the current tab's URL, configures activities and items, and shows
 // an activity view.
 - (void)shareCurrentPage {
-  self.sharePageStartTime = base::TimeTicks::Now();
-
   // Retrieve the current page's URL.
   __weak __typeof(self) weakSelf = self;
   activity_services::RetrieveCanonicalUrl(
@@ -172,12 +158,6 @@ const char kSharePageLatencyHistogram[] = "IOS.SharePageLatency";
   if (!data)
     return;
 
-  if (self.sharePageStartTime != base::TimeTicks()) {
-    UMA_HISTOGRAM_TIMES(kSharePageLatencyHistogram,
-                        base::TimeTicks::Now() - self.sharePageStartTime);
-    self.sharePageStartTime = base::TimeTicks();
-  }
-
   NSArray<ChromeActivityURLSource*>* items =
       [self.mediator activityItemsForData:data];
   NSArray* activities = [self.mediator applicationActivitiesForData:data];

tools/metrics/histograms/histograms_xml/ios/histograms.xml

@@ -759,6 +759,9 @@ reviews. Googlers can read more about this at go/gwsq-gerrit.
 </histogram>
 
 <histogram name="IOS.SharePageLatency" units="ms" expires_after="M77">
+  <obsolete>
+    Deprecated 12/2020 as it is no longer used for analysis.
+  </obsolete>
   <owner>pkl@chromium.org</owner>
   <summary>
     The latency in milliseconds between the start of the Share Page operation