When onPageFinished calls onNewPicture, pass null picture on SDK>=JB MR2.

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.content.Context;
 import android.content.Intent;
@@ skipping 388 matching lines @@
                 public void run() {
                     destroy();
                 }
             });
             return;
         }
 
         // Make sure that we do not trigger any callbacks after destruction
         mContentsClientAdapter.setWebChromeClient(null);
         mContentsClientAdapter.setWebViewClient(null);
-        mContentsClientAdapter.setPictureListener(null);
+        mContentsClientAdapter.setPictureListener(null, true);
         mContentsClientAdapter.setFindListener(null);
         mContentsClientAdapter.setDownloadListener(null);
 
         mAwContents.destroy();
     }
 
     @Override
     public void setNetworkAvailable(final boolean networkUp) {
         // Note that this purely toggles the JS navigator.online property.
         // It does not in affect chromium or network stack state in any way.
@@ skipping 867 matching lines @@
     public void setPictureListener(final WebView.PictureListener listener) {
         if (checkNeedsPost()) {
             mFactory.addTask(new Runnable() {
                 @Override
                 public void run() {
                     setPictureListener(listener);
                 }
             });
             return;
         }
-        mContentsClientAdapter.setPictureListener(listener);
-        mAwContents.enableOnNewPicture(
-                listener != null, mAppTargetSdkVersion >= Build.VERSION_CODES.JELLY_BEAN_MR2);
+        boolean invalidateOnly = mAppTargetSdkVersion >= Build.VERSION_CODES.JELLY_BEAN_MR2;
+        mContentsClientAdapter.setPictureListener(listener, invalidateOnly);
+        mAwContents.enableOnNewPicture(listener != null, invalidateOnly);
     }
 
     @Override
     public void addJavascriptInterface(final Object obj, final String interfaceName) {
         if (checkNeedsPost()) {
             mFactory.addTask(new Runnable() {
                 @Override
                 public void run() {
                     addJavascriptInterface(obj, interfaceName);
                 }
@@ skipping 952 matching lines @@
         mAwContents.extractSmartClipData(x, y, width, height);
     }
 
     // Implements SmartClipProvider
     @Override
     public void setSmartClipResultHandler(final Handler resultHandler) {
         checkThread();
         mAwContents.setSmartClipResultHandler(resultHandler);
     }
 }