Disable bottom toolbar home button in NTP

Bug: 904980
Change-Id: I8be16d85a204fcd306fd7d5ea4e2988295daab77
Reviewed-on: https://chromium-review.googlesource.com/c/1364340Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Pedro Amaral <amaralp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614835}

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

@@ -17,7 +17,11 @@ import android.view.View.OnCreateContextMenuListener;
 
 import org.chromium.base.ApiCompatibilityUtils;
 import org.chromium.chrome.R;
+import org.chromium.chrome.browser.ActivityTabProvider;
+import org.chromium.chrome.browser.ActivityTabProvider.ActivityTabTabObserver;
+import org.chromium.chrome.browser.ntp.NewTabPage;
 import org.chromium.chrome.browser.partnercustomizations.HomepageManager;
+import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.toolbar.ThemeColorProvider.ThemeColorObserver;
 import org.chromium.chrome.browser.util.FeatureUtilities;
 import org.chromium.ui.widget.ChromeImageButton;
@@ -33,6 +37,9 @@ public class HomeButton extends ChromeImageButton implements ThemeColorObserver,
     /** A provider that notifies components when the theme color changes.*/
     private ThemeColorProvider mThemeColorProvider;
 
+    /** The {@link sActivityTabTabObserver} used to know when the active page changed. */
+    private ActivityTabTabObserver mActivityTabTabObserver;
+
     public HomeButton(Context context, AttributeSet attrs) {
         super(context, attrs);
 
@@ -51,6 +58,10 @@ public class HomeButton extends ChromeImageButton implements ThemeColorObserver,
             mThemeColorProvider.removeObserver(this);
             mThemeColorProvider = null;
         }
+        if (mActivityTabTabObserver != null) {
+            mActivityTabTabObserver.destroy();
+            mActivityTabTabObserver = null;
+        }
     }
 
     public void setThemeColorProvider(ThemeColorProvider themeColorProvider) {
@@ -74,4 +85,25 @@ public class HomeButton extends ChromeImageButton implements ThemeColorObserver,
         HomepageManager.getInstance().setPrefHomepageEnabled(false);
         return true;
     }
+
+    public void setActivityTabProvider(ActivityTabProvider activityTabProvider) {
+        mActivityTabTabObserver = new ActivityTabTabObserver(activityTabProvider) {
+            @Override
+            public void onObservingDifferentTab(Tab tab) {
+                if (tab == null) return;
+                setEnabled(shouldEnableHome(tab));
+            }
+
+            @Override
+            public void onPageLoadFinished(Tab tab, String url) {
+                if (tab == null) return;
+                setEnabled(shouldEnableHome(tab));
+            }
+        };
+    }
+
+    private static boolean shouldEnableHome(Tab tab) {
+        if (!FeatureUtilities.isBottomToolbarEnabled()) return true;
+        return !NewTabPage.isNTPUrl(tab.getUrl());
+    }
 }

chrome/android/java/src/org/chromium/chrome/browser/toolbar/bottom/BrowsingModeBottomToolbarCoordinator.java

@@ -85,6 +85,7 @@ public class BrowsingModeBottomToolbarCoordinator {
 
         mHomeButton = toolbarRoot.findViewById(R.id.home_button);
         mHomeButton.setOnClickListener(homeButtonListener);
+        mHomeButton.setActivityTabProvider(tabProvider);
 
         mShareButton = toolbarRoot.findViewById(R.id.share_button);
         mShareButton.setOnClickListener(shareButtonListener);