Remove usage of Tab's |url| property from NewTabPageUMA utilities.

ios/chrome/browser/metrics/new_tab_page_uma.mm

 // Copyright 2016 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/metrics/new_tab_page_uma.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "components/google/core/browser/google_util.h"
 #include "ios/chrome/browser/browser_state/chrome_browser_state.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #import "ios/chrome/browser/tabs/tab.h"
 #import "ios/chrome/browser/tabs/tab_model.h"
 #import "ios/chrome/browser/tabs/tab_model_list.h"
 #include "url/gurl.h"
 
 namespace new_tab_page_uma {
 
-bool IsCurrentlyOnNTP(ios::ChromeBrowserState* browserState) {
-  TabModel* tabModel = GetLastActiveTabModelForChromeBrowserState(browserState);
-  return tabModel.currentTab &&
-         tabModel.currentTab.url == GURL(kChromeUINewTabURL);
+bool IsCurrentlyOnNTP(ios::ChromeBrowserState* browser_state) {
+  TabModel* tab_model =
+      GetLastActiveTabModelForChromeBrowserState(browser_state);
+  return tab_model.currentTab &&
+         tab_model.currentTab.visibleURL == GURL(kChromeUINewTabURL);

[kkhorimoto, 2017/04/14 20:34:33]

The old behavior would return a non-NTP URL if there was any navigation
occurring at all.  This updates the implementation slightly to return the
non-NTP URL only if there's a user-initiated load.

[Eugene But (OOO till 7-30), 2017/04/14 21:43:02]

Should this be lastCommittedURL? I think that old code was not correct.

[kkhorimoto, 2017/05/31 22:58:33]

For user-initiated loads, the web view will be shown immediately and the NTP
will be removed as soon as the pending item is created.  Thus, if the visible
item's URL is not the NTP, then the NTP is not currently being displayed.  For
renderer-initiated loads, the web view will be shown only after the load is
committed.  Using the visible URL makes sense to me because it's tightly coupled
to whether the NTP or the webview is currently displayed.

 }
 
 void RecordAction(ios::ChromeBrowserState* browserState, ActionType type) {
   DCHECK(browserState);
   if (!IsCurrentlyOnNTP(browserState) || browserState->IsOffTheRecord())
     return;
   base::HistogramBase* counter = base::Histogram::FactoryGet(
       "NewTabPage.ActioniOS", 0, NUM_ACTION_TYPES, NUM_ACTION_TYPES + 1,
       base::HistogramBase::kUmaTargetedHistogramFlag);
   counter->Add(type);
 }
 
 void RecordActionFromOmnibox(ios::ChromeBrowserState* browserState,
                              const GURL& url,
                              ui::PageTransition transition) {
   ui::PageTransition coreTransition = static_cast<ui::PageTransition>(
       transition & ui::PAGE_TRANSITION_CORE_MASK);
   if (PageTransitionCoreTypeIs(coreTransition, ui::PAGE_TRANSITION_GENERATED)) {
     RecordAction(browserState, ACTION_SEARCHED_USING_OMNIBOX);
   } else {
     if (google_util::IsGoogleHomePageUrl(GURL(url))) {
       RecordAction(browserState, ACTION_NAVIGATED_TO_GOOGLE_HOMEPAGE);
     } else {
       RecordAction(browserState, ACTION_NAVIGATED_USING_OMNIBOX);
     }
   }
 }
 }