Make it possible for the scroll offset delegate to intercept fling.

android_webview/lib/main/aw_main_delegate.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 "android_webview/lib/main/aw_main_delegate.h"
 
 #include "android_webview/browser/aw_content_browser_client.h"
 #include "android_webview/browser/gpu_memory_buffer_factory_impl.h"
 #include "android_webview/browser/scoped_allow_wait_for_legacy_web_view_api.h"
 #include "android_webview/lib/aw_browser_dependency_factory_impl.h"
@@ skipping 39 matching lines @@
       gpu_memory_buffer_factory_.get());
 
   CommandLine* cl = CommandLine::ForCurrentProcess();
   cl->AppendSwitch(switches::kEnableBeginFrameScheduling);
   if (!cl->HasSwitch("disable-map-image"))
     cl->AppendSwitch(cc::switches::kUseMapImage);
 
   // WebView uses the Android system's scrollbars and overscroll glow.
   cl->AppendSwitch(switches::kHideScrollbars);
   cl->AppendSwitch(switches::kDisableOverscrollEdgeEffect);
+  // WebView handles fling gestures Java-side.
+  cl->AppendSwitch(switches::kIgnoreRootLayerFlings);
 
   return false;
 }
 
 void AwMainDelegate::PreSandboxStartup() {
   // TODO(torne): When we have a separate renderer process, we need to handle
   // being passed open FDs for the resource paks here.
 }
 
 void AwMainDelegate::SandboxInitialized(const std::string& process_type) {
@@ skipping 49 matching lines @@
         AwBrowserContext* browser_context) {
   return AwGeolocationPermissionContext::Create(browser_context);
 }
 
 content::WebContentsViewDelegate* AwMainDelegate::CreateViewDelegate(
     content::WebContents* web_contents) {
   return AwWebContentsViewDelegate::Create(web_contents);
 }
 
 }  // namespace android_webview