customtabs: Don't cache the Tab in PageLoadMetricsObserver.

chrome/android/java/src/org/chromium/chrome/browser/customtabs/CustomTabActivity.java

 // Copyright 2015 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.customtabs;
 
 import android.app.PendingIntent;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ skipping 113 matching lines @@
 
     private boolean mIsClosing;
 
     // This boolean is used to do a hack in navigation history for
     // prerender and hidden tab loads with unmatching fragments.
     private boolean mIsFirstLoad;
 
     private static class PageLoadMetricsObserver implements PageLoadMetrics.Observer {
         private final CustomTabsConnection mConnection;
         private final CustomTabsSessionToken mSession;
-        private final Tab mTab;
+        private final WebContents mWebContents;
 
         public PageLoadMetricsObserver(CustomTabsConnection connection,
                 CustomTabsSessionToken session, Tab tab) {
             mConnection = connection;
             mSession = session;
-            mTab = tab;
+            mWebContents = tab.getWebContents();
         }
 
         @Override
         public void onFirstContentfulPaint(
                 WebContents webContents, long navigationStartTick, long firstContentfulPaintMs) {
-            if (webContents != mTab.getWebContents()) return;
+            if (webContents != mWebContents) return;
 
             mConnection.notifyPageLoadMetric(mSession, PageLoadMetrics.FIRST_CONTENTFUL_PAINT,
                     navigationStartTick, firstContentfulPaintMs);
         }
 
         @Override
         public void onLoadEventStart(
                 WebContents webContents, long navigationStartTick, long loadEventStartMs) {
-            if (webContents != mTab.getWebContents()) return;
+            if (webContents != mWebContents) return;
 
             mConnection.notifyPageLoadMetric(mSession, PageLoadMetrics.LOAD_EVENT_START,
                     navigationStartTick, loadEventStartMs);
         }
     }
 
     private static class CustomTabCreator extends ChromeTabCreator {
         private final boolean mSupportsUrlBarHiding;
         private final boolean mIsOpenedByChrome;
         private final BrowserStateBrowserControlsVisibilityDelegate mVisibilityDelegate;
@@ skipping 976 matching lines @@
         Intent intent = ChromeLauncherActivity.createCustomTabActivityIntent(
                 context, customTabIntent.intent, false);
         intent.setPackage(context.getPackageName());
         intent.putExtra(CustomTabIntentDataProvider.EXTRA_IS_INFO_PAGE, true);
         intent.putExtra(Browser.EXTRA_APPLICATION_ID, context.getPackageName());
         IntentHandler.addTrustedIntentExtras(intent);
 
         context.startActivity(intent);
     }
 }