Add runtime setting to force passive event listeners.

content/browser/renderer_host/render_process_host_impl.cc

 // Copyright 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.
 
 // Represents the browser side of the browser <--> renderer communication
 // channel. There will be one RenderProcessHost per renderer process.
 
 #include "content/browser/renderer_host/render_process_host_impl.h"
 
 #include <algorithm>
@@ skipping 1404 matching lines @@
     switches::kJavaScriptFlags,
     switches::kLoggingLevel,
     switches::kMainFrameResizesAreOrientationChanges,
     switches::kMaxUntiledLayerWidth,
     switches::kMaxUntiledLayerHeight,
     switches::kMemoryMetrics,
     switches::kMojoLocalStorage,
     switches::kNoReferrers,
     switches::kNoSandbox,
     switches::kOverridePluginPowerSaverForTesting,
+    switches::kPassiveListenersDefault,
     switches::kPpapiInProcess,
     switches::kProfilerTiming,
     switches::kReducedReferrerGranularity,
     switches::kReduceSecurityForTesting,
     switches::kRegisterPepperPlugins,
     switches::kRendererStartupDialog,
     switches::kRootLayerScrolls,
     switches::kShowPaintRects,
     switches::kSitePerProcess,
     switches::kStatsCollectionController,
@@ skipping 1317 matching lines @@
 
     // Skip widgets in other processes.
     if (rvh->GetProcess()->GetID() != GetID())
       continue;
 
     rvh->OnWebkitPreferencesChanged();
   }
 }
 
 }  // namespace content