Disable compositing asserts when gesture scrolling on main thread

third_party/WebKit/Source/core/input/ScrollManager.cpp

 // Copyright 2016 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 "core/input/ScrollManager.h"
 
 #include "core/dom/DOMNodeIds.h"
 #include "core/events/GestureEvent.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
@@ skipping 176 matching lines @@
     scrollState.distributeToScrollChainDescendant();
 }
 
 WebInputEventResult ScrollManager::handleGestureScrollBegin(const PlatformGestureEvent& gestureEvent)
 {
     Document* document = m_frame->document();
 
     if (document->layoutViewItem().isNull())
         return WebInputEventResult::NotHandled;
 
-    FrameView* view = m_frame->view();
-    if (!view)
-        return WebInputEventResult::NotHandled;
-
     // If there's no layoutObject on the node, send the event to the nearest ancestor with a layoutObject.
     // Needed for <option> and <optgroup> elements so we can touch scroll <select>s
     while (m_scrollGestureHandlingNode && !m_scrollGestureHandlingNode->layoutObject())
         m_scrollGestureHandlingNode = m_scrollGestureHandlingNode->parentOrShadowHostNode();
 
     if (!m_scrollGestureHandlingNode)
         m_scrollGestureHandlingNode = m_frame->document()->documentElement();
 
     if (!m_scrollGestureHandlingNode)
         return WebInputEventResult::NotHandled;
@@ skipping 138 matching lines @@
 
     if (!node.isElementNode())
         return false;
 
     return node.isSameNode(m_frame->document()->effectiveRootScroller());
 }
 
 
 WebInputEventResult ScrollManager::handleGestureScrollEvent(const PlatformGestureEvent& gestureEvent)
 {
+    if (!m_frame->view())
+        return WebInputEventResult::NotHandled;
+
     Node* eventTarget = nullptr;
     Scrollbar* scrollbar = nullptr;
     if (gestureEvent.type() != PlatformEvent::GestureScrollBegin) {
         scrollbar = m_scrollbarHandlingScrollGesture.get();
         eventTarget = m_scrollGestureHandlingNode.get();
     }
 
     if (!eventTarget) {
         Document* document = m_frame->document();
         if (document->layoutViewItem().isNull())
@@ skipping 135 matching lines @@
 DEFINE_TRACE(ScrollManager)
 {
     visitor->trace(m_frame);
     visitor->trace(m_scrollGestureHandlingNode);
     visitor->trace(m_previousGestureScrolledNode);
     visitor->trace(m_scrollbarHandlingScrollGesture);
     visitor->trace(m_resizeScrollableArea);
 }
 
 } // namespace blink