Set deceleration rate for WKWebView

ios/web/web_state/web_view_internal_creation_util.mm

 // Copyright 2014 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.
 
 #import "ios/web/web_state/web_view_internal_creation_util.h"
 
 #import <objc/runtime.h>
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
@@ skipping 169 matching lines @@
   bool previous_allow_web_view_creation_value = gAllowWebViewCreation;
   gAllowWebViewCreation = true;
 #endif
   WKWebView* result =
       [[WKWebView alloc] initWithFrame:frame configuration:configuration];
 #if !defined(NDEBUG)
   gAllowWebViewCreation = previous_allow_web_view_creation_value;
 #endif
   PostWKWebViewCreation(result, browser_state);
 
+  // By default the web view uses a very sluggish scroll speed. Set it to a more
+  // reasonable value.
+  result.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;
+
   return result;
 }
 
 NSUInteger GetActiveWKWebViewsCount() {
 #if defined(NDEBUG)
   // This should not be used in release builds.
   CHECK(0);
   return 0;
 #else
   return GetActiveWKWebViewCounter().Size();
@@ skipping 58 matching lines @@
     if (!gAllowWebViewCreation) {
       gWebViewsNeedActiveStateManager =
           GetWebClient()->WebViewsNeedActiveStateManager();
     }
   });
   return gAllowWebViewCreation;
 }
 #endif
 
 }  // namespace web