Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/pinch_zoom_scrollbar_painter.cc

+// Copyright 2013 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 "cc/pinch_zoom_scrollbar_painter.h"
+
+#include "third_party/skia/include/core/SkCanvas.h"
+#include "ui/gfx/rect.h"
+
+namespace cc {
+
+PinchZoomScrollbarPainter::~PinchZoomScrollbarPainter() {}
+
+void PinchZoomScrollbarPainter::PaintScrollbarBackground(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintTrackBackground(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintBackTrackPart(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintForwardTrackPart(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintBackButtonStart(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintBackButtonEnd(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintForwardButtonStart(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintForwardButtonEnd(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintTickmarks(SkCanvas*, const gfx::Rect&) {
+}
+
+void PinchZoomScrollbarPainter::PaintThumb(SkCanvas* canvas,
+    const gfx::Rect& thumb_rect) {
+  canvas->clear(SkColorSetARGB(0, 0, 0, 0));
+  SkPaint paint;
+  // Below 255 refers to blue, not red, but we do this to avoid an
+  // explicit swizzle.
+  paint.setColor(SkColorSetARGB(128, 255, 0, 0));
+  SkScalar border = 2;
+  SkScalar corner_radius = 2;
+  SkRect rect = SkRect::MakeXYWH(border, border,
+                                 thumb_rect.width() - 2 * border,
+                                 thumb_rect.height() - 2 * border);
+  canvas->drawRoundRect(rect, corner_radius, corner_radius, paint);
+}
+
+}  // namespace cc