Limit PassiveDocumentEventListeners to touch and make it experimental

content/child/runtime_features.cc

 // Copyright 2013 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/child/runtime_features.h"
 
 #include <vector>
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
@@ skipping 214 matching lines @@
 
   if (base::FeatureList::IsEnabled(features::kDocumentWriteEvaluator))
     WebRuntimeFeatures::enableDocumentWriteEvaluator(true);
 
   WebRuntimeFeatures::enableMediaDocumentDownloadButton(
       base::FeatureList::IsEnabled(features::kMediaDocumentDownloadButton));
 
   if (base::FeatureList::IsEnabled(features::kPointerEvents))
     WebRuntimeFeatures::enablePointerEvent(true);
 
-  WebRuntimeFeatures::enablePassiveDocumentEventListeners(
-      base::FeatureList::IsEnabled(features::kPassiveDocumentEventListeners));
+  if (base::FeatureList::IsEnabled(features::kPassiveDocumentEventListeners))
+    WebRuntimeFeatures::enablePassiveDocumentEventListeners(true);
 
   WebRuntimeFeatures::enableFeatureFromString(
       "FontCacheScaling",
       base::FeatureList::IsEnabled(features::kFontCacheScaling));
 
   if (!base::FeatureList::IsEnabled(features::kPaintOptimizations))
     WebRuntimeFeatures::enableFeatureFromString("PaintOptimizations", false);
 
   if (base::FeatureList::IsEnabled(features::kParseHTMLOnMainThread))
     WebRuntimeFeatures::enableFeatureFromString("ParseHTMLOnMainThread", true);
@@ skipping 13 matching lines @@
   if (command_line.HasSwitch(switches::kDisableBlinkFeatures)) {
     std::vector<std::string> disabled_features = base::SplitString(
         command_line.GetSwitchValueASCII(switches::kDisableBlinkFeatures),
         ",", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
     for (const std::string& feature : disabled_features)
       WebRuntimeFeatures::enableFeatureFromString(feature, false);
   }
 }
 
 }  // namespace content