Fix GetPartSize to account for customized themes.

ui/native_theme/native_theme_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 "ui/native_theme/native_theme_win.h"
 
 #include <windows.h>
 #include <uxtheme.h>
 #include <vsstyle.h>
 #include <vssym32.h>
@@ skipping 215 matching lines @@
 }
 
 gfx::Size NativeThemeWin::GetPartSize(Part part,
                                       State state,
                                       const ExtraParams& extra) const {
   if (IsNewMenuStyleEnabled()) {
     gfx::Size size = CommonThemeGetPartSize(part, state, extra);
     if (!size.IsEmpty())
       return size;
   }
+
+  // The GetThemePartSize call below returns the default size without
+  // accounting for user customization (crbug/218291).
   SIZE size;
+  switch (part) {
+    case kScrollbarDownArrow:
+    case kScrollbarLeftArrow:
+    case kScrollbarRightArrow:
+    case kScrollbarUpArrow:
+    case kScrollbarHorizontalThumb:
+    case kScrollbarVerticalThumb:
+    case kScrollbarHorizontalTrack:
+    case kScrollbarVerticalTrack:
+      size.cx = size.cy = ui::win::GetSystemMetricsInDIP(SM_CXVSCROLL);
+      return gfx::Size(size.cx, size.cy);
+  }
+
   int part_id = GetWindowsPart(part, state, extra);
   int state_id = GetWindowsState(part, state, extra);
 
   HDC hdc = GetDC(NULL);
   HRESULT hr = GetThemePartSize(GetThemeName(part), hdc, part_id, state_id,
                                 NULL, TS_TRUE, &size);
   ReleaseDC(NULL, hdc);
 
   if (FAILED(hr)) {
     // TODO(rogerta): For now, we need to support radio buttons and checkboxes
     // when theming is not enabled.  Support for other parts can be added
     // if/when needed.
     switch (part) {
       case kCheckbox:
       case kRadio:
         // TODO(rogerta): I was not able to find any API to get the default
         // size of these controls, so determined these values empirically.
         size.cx = 13;
         size.cy = 13;
         break;
-      case kScrollbarDownArrow:
-      case kScrollbarLeftArrow:
-      case kScrollbarRightArrow:
-      case kScrollbarUpArrow:
-      case kScrollbarHorizontalThumb:
-      case kScrollbarVerticalThumb:
-      case kScrollbarHorizontalTrack:
-      case kScrollbarVerticalTrack:
-        size.cx = size.cy = GetSystemMetrics(SM_CXVSCROLL) /
-            ui::win::GetDeviceScaleFactor();
-        break;
       default:
         size.cx = 0;
         size.cy = 0;
         break;
     }
   }
 
   return gfx::Size(size.cx, size.cy);
 }
 
@@ skipping 1793 matching lines @@
     handle = open_theme_(NULL, L"Spin");
     break;
   default:
     NOTREACHED();
   }
   theme_handles_[theme_name] = handle;
   return handle;
 }
 
 }  // namespace ui