Use float for scroll offset.

third_party/WebKit/Source/web/DevToolsEmulator.cpp

 // Copyright 2015 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 "web/DevToolsEmulator.h"
 
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
 #include "core/frame/VisualViewport.h"
@@ skipping 481 matching lines @@
   // compositor-side pinch handling is not enabled. See http://crbug.com/138003.
   bool isPinch = inputEvent.type == WebInputEvent::GesturePinchBegin ||
                  inputEvent.type == WebInputEvent::GesturePinchUpdate ||
                  inputEvent.type == WebInputEvent::GesturePinchEnd;
   if (isPinch && m_touchEventEmulationEnabled) {
     FrameView* frameView = page->deprecatedLocalMainFrame()->view();
     PlatformGestureEventBuilder gestureEvent(
         frameView, static_cast<const WebGestureEvent&>(inputEvent));
     float pageScaleFactor = page->pageScaleFactor();
     if (gestureEvent.type() == PlatformEvent::GesturePinchBegin) {
-      m_lastPinchAnchorCss = wrapUnique(
-          new IntPoint(frameView->scrollPosition() + gestureEvent.position()));
+      m_lastPinchAnchorCss = wrapUnique(new IntPoint(roundedIntPoint(
+          gestureEvent.position() + frameView->scrollOffset())));
       m_lastPinchAnchorDip = wrapUnique(new IntPoint(gestureEvent.position()));
       m_lastPinchAnchorDip->scale(pageScaleFactor, pageScaleFactor);
     }
     if (gestureEvent.type() == PlatformEvent::GesturePinchUpdate &&
         m_lastPinchAnchorCss) {
       float newPageScaleFactor = pageScaleFactor * gestureEvent.scale();
       IntPoint anchorCss(*m_lastPinchAnchorDip.get());
       anchorCss.scale(1.f / newPageScaleFactor, 1.f / newPageScaleFactor);
       m_webViewImpl->setPageScaleFactor(newPageScaleFactor);
       m_webViewImpl->mainFrame()->setScrollOffset(
           toIntSize(*m_lastPinchAnchorCss.get() - toIntSize(anchorCss)));
     }
     if (gestureEvent.type() == PlatformEvent::GesturePinchEnd) {
       m_lastPinchAnchorCss.reset();
       m_lastPinchAnchorDip.reset();
     }
     return true;
   }
 
   return false;
 }
 
 }  // namespace blink