android webview: setShouldReuseGlobalForUnownedMainFrame

android_webview/glue/java/src/com/android/webview/chromium/WebViewChromium.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 com.android.webview.chromium;
 
 import android.annotation.SuppressLint;
 import android.annotation.TargetApi;
 import android.app.assist.AssistStructure.ViewNode;
 import android.content.Context;
@@ skipping 216 matching lines @@
             checkThread();
         } else if (!mFactory.hasStarted()) {
             if (Looper.myLooper() == Looper.getMainLooper()) {
                 mFactory.startYourEngines(true);
             }
         }
 
         final boolean isAccessFromFileURLsGrantedByDefault =
                 mAppTargetSdkVersion < Build.VERSION_CODES.JELLY_BEAN;
         final boolean areLegacyQuirksEnabled = mAppTargetSdkVersion < Build.VERSION_CODES.KITKAT;
+        final boolean allowEmptyDocumentPersistence = mAppTargetSdkVersion <= Build.VERSION_CODES.M;
 
         mContentsClientAdapter =
                 new WebViewContentsClientAdapter(mWebView, mContext, mFactory.getWebViewDelegate());
-        mWebSettings = new ContentSettingsAdapter(new AwSettings(
-                mContext, isAccessFromFileURLsGrantedByDefault, areLegacyQuirksEnabled));
+        mWebSettings = new ContentSettingsAdapter(
+                new AwSettings(mContext, isAccessFromFileURLsGrantedByDefault,
+                        areLegacyQuirksEnabled, allowEmptyDocumentPersistence));
 
         if (mAppTargetSdkVersion < Build.VERSION_CODES.LOLLIPOP) {
             // Prior to Lollipop we always allowed third party cookies and mixed content.
             mWebSettings.setMixedContentMode(WebSettings.MIXED_CONTENT_ALWAYS_ALLOW);
             mWebSettings.setAcceptThirdPartyCookies(true);
             mWebSettings.getAwSettings().setZeroLayoutHeightDisablesViewportQuirk(true);
         }
 
         mRunQueue.addTask(new Runnable() {
             @Override
@@ skipping 2102 matching lines @@
         mAwContents.extractSmartClipData(x, y, width, height);
     }
 
     // Implements SmartClipProvider
     @Override
     public void setSmartClipResultHandler(final Handler resultHandler) {
         checkThread();
         mAwContents.setSmartClipResultHandler(resultHandler);
     }
 }