Remove unused histogram

Bug: 643554
Change-Id: I30b9e73aa3b5f6424b81614c5a9ae8e3466f37f8
Reviewed-on: https://chromium-review.googlesource.com/c/1440701
Auto-Submit: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#628481}

chrome/browser/local_discovery/service_discovery_client_mac.mm

@@ -233,10 +233,7 @@ ServiceWatcherImplMac::NetServiceBrowserContainer::DiscoverOnDiscoveryThread() {
   DVLOG(1) << "Listening for service type '" << [type UTF8String]
            << "' on domain '" << [domain UTF8String] << "'";
 
-  base::Time start_time = base::Time::Now();
   [browser_ searchForServicesOfType:type inDomain:domain];
-  UMA_HISTOGRAM_TIMES("LocalDiscovery.MacBrowseCallTimes",
-                      base::Time::Now() - start_time);
 }
 
 void ServiceWatcherImplMac::NetServiceBrowserContainer::OnServicesUpdate(