Add metrics for triggering of JS dialogs on Android.

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

 // Copyright 2014 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.
 
 package org.chromium.chrome.browser.tab;
 
 import android.annotation.SuppressLint;
 import android.app.Activity;
 import android.app.Application;
 import android.content.Context;
 import android.content.Intent;
 import android.content.res.Resources;
 import android.graphics.Bitmap;
 import android.graphics.Color;
 import android.graphics.Rect;
 import android.net.Uri;
 import android.os.Bundle;
 import android.provider.Browser;
 import android.support.annotation.Nullable;
+import android.support.v4.view.ViewCompat;
 import android.text.TextUtils;
 import android.util.Log;
 import android.view.ContextThemeWrapper;
 import android.view.View;
 import android.view.View.OnClickListener;
 import android.view.ViewGroup;
 import android.view.accessibility.AccessibilityEvent;
 import android.widget.FrameLayout;
 import android.widget.FrameLayout.LayoutParams;
 
@@ skipping 2201 matching lines @@
     }
 
     /**
      * @return Whether or not the tab is hidden.
      */
     public boolean isHidden() {
         return mIsHidden;
     }
 
     /**
+     * @return Whether the tab can currently be interacted with by the user.  This requires the
+     *         view to be visible and in a state the user can manipulate the tab (i.e. not in
+     *         something like the phone tab switcher).

[gone, 2017/01/13 18:54:37]

How does this work for a tablet, where the tab might be dead but is still
visible on the strip?  Maybe the comment can be clarified so that it implies
that the user is interacting with the web page displayed in the tab?

[Ted C, 2017/01/20 16:57:46]

Updated the comment to clarify the tab's view needs to be visible (since it
doesn't
necessarily need to be web contents).

+     */
+    @CalledByNative
+    public boolean isUserInteractable() {
+        return !mIsHidden && ViewCompat.isAttachedToWindow(getView());
+    }
+
+    /**
      * @return Whether or not the tab is in the closing process.
      */
     public boolean isClosing() {
         return mIsClosing;
     }
 
     /**
      * @param closing Whether or not the tab is in the closing process.
      */
     public void setClosing(boolean closing) {
@@ skipping 949 matching lines @@
     private native void nativeLoadOriginalImage(long nativeTabAndroid);
     private native long nativeGetBookmarkId(long nativeTabAndroid, boolean onlyEditable);
     private native boolean nativeIsOfflinePage(long nativeTabAndroid);
     private native OfflinePageItem nativeGetOfflinePage(long nativeTabAndroid);
     private native void nativeSetInterceptNavigationDelegate(long nativeTabAndroid,
             InterceptNavigationDelegate delegate);
     private native void nativeAttachToTabContentManager(long nativeTabAndroid,
             TabContentManager tabContentManager);
     private native boolean nativeHasPrerenderedUrl(long nativeTabAndroid, String url);
 }