[Custom tab]Fix a bug that clicking media notification opens blank tab

chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java

Index: chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
index 9f2b7daf463b28f2dd3c1bee1982bbfc9d878fdc..67f0e5b6558ee4a6b681fb92be9ff94a7f705b05 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/tab/Tab.java
@@ -50,6 +50,7 @@ import org.chromium.chrome.browser.contextmenu.ContextMenuParams;
 import org.chromium.chrome.browser.contextmenu.ContextMenuPopulator;
 import org.chromium.chrome.browser.contextmenu.ContextMenuPopulatorWrapper;
 import org.chromium.chrome.browser.contextmenu.EmptyChromeContextMenuItemDelegate;
+import org.chromium.chrome.browser.customtabs.CustomTabActivity;
 import org.chromium.chrome.browser.fullscreen.FullscreenManager;
 import org.chromium.chrome.browser.help.HelpAndFeedback;
 import org.chromium.chrome.browser.infobar.InfoBarContainer;
@@ -86,6 +87,7 @@ import org.chromium.ui.base.PageTransition;
 import org.chromium.ui.base.WindowAndroid;
 import org.chromium.ui.gfx.DeviceDisplayInfo;
 
+import java.lang.ref.WeakReference;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.List;
@@ -2842,9 +2844,21 @@ public class Tab implements ViewGroup.OnHierarchyChangeListener,
     }
 
     /**
-     * Returns an Intent that tells Chrome to open a Tab with a particular ID.
+     * @return Intent that tells Chrome to bring an Activity for a particular Tab back to the
+     *         foreground, or null if this isn't possible.
      */
     public static Intent createBringTabToFrontIntent(int tabId) {
+        // Iterate through all {@link CustomTab}s and check whether the given tabId belongs to a
+        // {@link CustomTab}. If so, return null as the client app's task cannot be foregrounded.
+        List<WeakReference<Activity>> list = ApplicationStatus.getRunningActivities();
+        for (WeakReference<Activity> ref : list) {
+            Activity activity = ref.get();
+            if (activity instanceof CustomTabActivity
+                    && tabId == ((CustomTabActivity) activity).getActivityTab().getId()) {
+                return null;
+            }
+        }
+
         String packageName = ApplicationStatus.getApplicationContext().getPackageName();
         Intent intent = new Intent(Intent.ACTION_MAIN);
         intent.putExtra(Browser.EXTRA_APPLICATION_ID, packageName);