Fix backing store scrolling on Windows in high-DPI mode.

content/browser/renderer_host/render_widget_host_view_win.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 "content/browser/renderer_host/render_widget_host_view_win.h"
 
 #include <InputScope.h>
 
 #include <algorithm>
 #include <map>
@@ skipping 718 matching lines @@
 
   for (size_t i = 0; i < copy_rects.size(); ++i) {
     gfx::Rect pixel_rect = ui::win::DIPToScreenRect(copy_rects[i]);
     // Damage might not be DIP aligned.
     pixel_rect.Inset(-1, -1);
     RECT bounds = pixel_rect.ToRECT();
     InvalidateRect(&bounds, false);
   }
 
   if (!scroll_rect.IsEmpty()) {
-    RECT clip_rect = scroll_rect.ToRECT();
-    ScrollWindowEx(scroll_delta.x(), scroll_delta.y(), NULL, &clip_rect,
-                   NULL, NULL, SW_INVALIDATE);
+    gfx::Rect pixel_rect = ui::win::DIPToScreenRect(scroll_rect);
+    // Damage might not be DIP aligned.
+    pixel_rect.Inset(-1, -1);
+    RECT clip_rect = pixel_rect.ToRECT();
+    float scale = ui::win::GetDeviceScaleFactor();
+    int dx = static_cast<int>(scale * scroll_delta.x());
+    int dy = static_cast<int>(scale * scroll_delta.y());
+    ScrollWindowEx(dx, dy, NULL, &clip_rect, NULL, NULL, SW_INVALIDATE);
   }
 
   if (!about_to_validate_and_paint_)
     Redraw();
 }
 
 void RenderWidgetHostViewWin::RenderViewGone(base::TerminationStatus status,
                                              int error_code) {
   UpdateCursorIfOverSelf();
   Destroy();
@@ skipping 2344 matching lines @@
   return new RenderWidgetHostViewWin(widget);
 }
 
 // static
 void RenderWidgetHostViewPort::GetDefaultScreenInfo(
       WebKit::WebScreenInfo* results) {
   GetScreenInfoForWindow(results, 0);
 }
 
 }  // namespace content