[duet] Check go-to tab when no active tab presents

Home page button seems enabled for a while on switching between tabs.
It is because during transition between views, HomeButton only check
the active tab, if no active tab, HomeButton did not check go-to
tab. In this CL, HomeButton will check go-to tab if no active tab.


Bug: 935266
Change-Id: I59f5a617ebefce21b461fbcbf95ca0d04c186ceb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1873396
Commit-Queue: Gang Wu <gangwu@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709794}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/HomeButton.java

@@ -121,7 +121,7 @@ public class HomeButton extends ChromeImageButton
 
     @Override
     public void onHomepageStateUpdated() {
-        updateButtonEnabledState();
+        updateButtonEnabledState(null);
     }
 
     public void setActivityTabProvider(ActivityTabProvider activityTabProvider) {
@@ -129,12 +129,14 @@ public class HomeButton extends ChromeImageButton
         mActivityTabTabObserver = new ActivityTabTabObserver(activityTabProvider) {
             @Override
             public void onObservingDifferentTab(Tab tab) {
-                updateButtonEnabledState();
+                if (tab == null) return;
+                updateButtonEnabledState(tab);
             }
 
             @Override
             public void onUpdateUrl(Tab tab, String url) {
-                updateButtonEnabledState();
+                if (tab == null) return;
+                updateButtonEnabledState(tab);
             }
         };
     }
@@ -142,23 +144,45 @@ public class HomeButton extends ChromeImageButton
     /**
      * Menu button is enabled when not in NTP or if in NTP and homepage is enabled and set to
      * somewhere other than the NTP.
+     * @param tab The notifying {@link Tab} that might be selected soon, this is a hint that a tab
+     *         change is likely.
      */
-    private void updateButtonEnabledState() {
+    private void updateButtonEnabledState(Tab tab) {
         // New tab page button takes precedence over homepage.
         final boolean isHomepageEnabled = HomepageManager.isHomepageEnabled();
-        final boolean isEnabled = !isActiveTabNTP()
-                || (isHomepageEnabled && !NewTabPage.isNTPUrl(HomepageManager.getHomepageUri()));
+
+        boolean isEnabled;
+        if (getActiveTab() != null) {
+            // Now tab shows a webpage, let's check if the webpage is not the NTP, or the webpage is
+            // NTP but homepage is not NTP.
+            isEnabled = !isTabNTP(getActiveTab())
+                    || (isHomepageEnabled
+                            && !NewTabPage.isNTPUrl(HomepageManager.getHomepageUri()));
+        } else {
+            // There is no active tab, which means tab is in transition, ex tab swither view to tab
+            // view, or from one tab to another tab.
+            isEnabled = !isTabNTP(tab);
+        }
         setEnabled(isEnabled);
         if (mWrapper != null) mWrapper.setEnabled(isEnabled);
         if (mLabel != null) mLabel.setEnabled(isEnabled);
     }
 
-    private boolean isActiveTabNTP() {
-        if (mActivityTabProvider == null) return false;
+    /**
+     * Check if the provided tab is NTP. The tab is a hint that
+     * @param tab The notifying {@link Tab} that might be selected soon, this is a hint that a tab
+     *         change is likely.
+     */
+    private boolean isTabNTP(Tab tab) {
+        return tab != null && NewTabPage.isNTPUrl(tab.getUrl());
+    }
 
-        final Tab tab = mActivityTabProvider.get();
-        if (tab == null) return false;
+    /**
+     * Return the active tab. If no active tab is shown, return null.
+     */
+    private Tab getActiveTab() {
+        if (mActivityTabProvider == null) return null;
 
-        return NewTabPage.isNTPUrl(tab.getUrl());
+        return mActivityTabProvider.get();
     }
 }