Bug 1534213 - Reduce the number of WebpageItemRow layout refreshes; r=JanH

Previously, WebpageItemRow's layout would be updated everytime a new Tab for
it's url would be ADDED/CLOSED/LOCATION_CHANGED to force a recheck of the need
to show the "Switch to tab hint".
To prevent multiple layout refreshes for every such event we will check the
current display status of the "Switch to tab hint" against the newly computed
value after an ADDED/CLOSED/LOCATION_CHANGED event was received.
Eagerly changing the value for 'switchToTabHintShown' along with informing
about the need for layout refresh to prevent any race conditions between
receiving more events and actualy refreshing the layout.
(In my tests I saw ADDED/LOCATION_CHANGE refreshing the same layout needlessly)

Differential Revision: https://phabricator.services.mozilla.com/D24013

--HG--
extra : moz-landing-system : lando

mobile/android/base/java/org/mozilla/gecko/activitystream/homepanel/stream/WebpageItemRow.java

@@ -40,6 +40,7 @@ public class WebpageItemRow extends StreamViewHolder implements Tabs.OnTabsChang
     private WebpageRowModel webpageModel;
     private OnContentChangedListener contentChangedListener;
     private int position;
+    private boolean switchToTabHintShown;
 
     private final StreamOverridablePageIconLayout pageIconLayout;
     private final TextView pageDomainView;
@@ -95,8 +96,8 @@ public class WebpageItemRow extends StreamViewHolder implements Tabs.OnTabsChang
         updatePageDomain();
         pageIconLayout.updateIcon(model.getUrl(), model.getImageUrl());
 
-        final boolean isTabOpenedForItem = isTabOpenedForItem();
-        switchToTabHint.setVisibility(isTabOpenedForItem ? View.VISIBLE : View.GONE);
+        switchToTabHintShown = isTabOpenedForItem();
+        switchToTabHint.setVisibility(switchToTabHintShown ? View.VISIBLE : View.GONE);
     }
 
     public void initResources() {
@@ -218,7 +219,9 @@ public class WebpageItemRow extends StreamViewHolder implements Tabs.OnTabsChang
         // because they can be about:reader URLs if the current or old tab page was a reader view
         final String tabUrl = ReaderModeUtils.stripAboutReaderUrl(tab.getURL());
         final String previousTabUrl = ReaderModeUtils.stripAboutReaderUrl(data);
-        if (itemUrl.equals(tabUrl) || itemUrl.equals(previousTabUrl)) {
+        if ((itemUrl.equals(tabUrl) || itemUrl.equals(previousTabUrl)) &&
+                (switchToTabHintShown != isTabOpenedForItem())) {
+            switchToTabHintShown = !switchToTabHintShown;
             notifyListenerAboutContentChange();
         }
     }