[Android WebView] make spellcheck off by default and opt-in using spellcheck="true" attribute.

content/renderer/render_view_impl.cc

 // Copyright (c) 2012 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.
 
 #include "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <memory>
 
@@ skipping 1135 matching lines @@
   // Force preload=none and disable autoplay on older or low end Android
   // platforms because their media pipelines are not stable enough to handle
   // concurrent elements. See http://crbug.com/612909, http://crbug.com/622826.
   const bool is_low_end_device =
       base::android::BuildInfo::GetInstance()->sdk_int() <=
           base::android::SDK_VERSION_JELLY_BEAN_MR2 ||
       base::SysInfo::IsLowEndDevice();
   settings->setForcePreloadNoneForMediaElements(is_low_end_device);
   WebRuntimeFeatures::enableAutoplayMutedVideos(
       prefs.autoplay_muted_videos_enabled && !is_low_end_device);
+  settings->setSpellCheckEnabledByDefault(prefs.spellcheck_enabled_by_default);
 #endif
 
   settings->setAutoplayExperimentMode(
       blink::WebString::fromUTF8(prefs.autoplay_experiment_mode));
 
   settings->setViewportEnabled(prefs.viewport_enabled);
   settings->setViewportMetaEnabled(prefs.viewport_meta_enabled);
   settings->setShrinksViewportContentToFit(
         prefs.shrinks_viewport_contents_to_fit);
   settings->setViewportStyle(
@@ skipping 1852 matching lines @@
   if (IsUseZoomForDSFEnabled()) {
     webview()->setZoomFactorForDeviceScaleFactor(device_scale_factor_);
   } else {
     webview()->setDeviceScaleFactor(device_scale_factor_);
   }
   webview()->settings()->setPreferCompositingToLCDTextEnabled(
       PreferCompositingToLCDText(compositor_deps_, device_scale_factor_));
 }
 
 }  // namespace content