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

cc/pinch_zoom_scrollbar.cc

+#include "cc/pinch_zoom_scrollbar.h"
+
+#include "cc/layer.h"
+#include "cc/layer_tree_host.h"
+
+namespace cc {
+
+PinchZoomScrollbar::PinchZoomScrollbar(
+    WebKit::WebScrollbar::Orientation orientation, LayerTreeHost* owner)
+  : orientation_(orientation),
+    owner_(owner) {
+  DCHECK(owner_);
+}
+
+
+bool PinchZoomScrollbar::isOverlay() const { return true; }
+
+int PinchZoomScrollbar::value() const {
+  Layer* rootScrollLayer = owner_->rootScrollLayer();
+  if (!rootScrollLayer)
+    return 0;
+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return rootScrollLayer->scrollOffset().x();
+  else
+    return rootScrollLayer->scrollOffset().y();
+}
+
+WebKit::WebPoint PinchZoomScrollbar::location() const {
+  return WebKit::WebPoint();
+}
+
+WebKit::WebSize PinchZoomScrollbar::size() const {
+  gfx::Size viewportSize = owner_->layoutViewportSize();
+  gfx::Size size;
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    size = gfx::Size(viewportSize.width() - kTrackWidth, kTrackWidth);
+  else
+    size = gfx::Size(kTrackWidth, viewportSize.height() - kTrackWidth);
+  return WebKit::WebSize(size);
+}
+
+bool PinchZoomScrollbar::enabled() const {
+    return true;
+}
+
+int PinchZoomScrollbar::maximum() const {
+  gfx::Size size = owner_->layoutViewportSize();
+  Layer* rootScrollLayer = owner_->rootScrollLayer();
+  if (!rootScrollLayer)
+    return 0;
+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return rootScrollLayer->contentBounds().width() - size.width();
+  else
+    return rootScrollLayer->contentBounds().height() - size.height();
+}
+
+int PinchZoomScrollbar::totalSize() const {
+  Layer* rootScrollLayer = owner_->rootScrollLayer();
+  gfx::Size size;
+  if (rootScrollLayer)
+    size = rootScrollLayer->contentBounds();
+  else
+    size = owner_->layoutViewportSize();
+
+  if (orientation_ == WebKit::WebScrollbar::Horizontal)
+    return size.width();
+  else
+    return size.height();
+}
+
+bool PinchZoomScrollbar::isScrollViewScrollbar() const {
+    return false;
+}
+
+bool PinchZoomScrollbar::isScrollableAreaActive() const {
+    return true;
+}
+
+WebKit::WebScrollbar::ScrollbarControlSize PinchZoomScrollbar::controlSize() const {
+    return WebKit::WebScrollbar::SmallScrollbar;
+}
+
+WebKit::WebScrollbar::ScrollbarPart PinchZoomScrollbar::pressedPart() const {
+    return WebKit::WebScrollbar::NoPart;
+}
+
+WebKit::WebScrollbar::ScrollbarPart PinchZoomScrollbar::hoveredPart() const {
+    return WebKit::WebScrollbar::NoPart;
+}
+
+WebKit::WebScrollbar::ScrollbarOverlayStyle PinchZoomScrollbar::scrollbarOverlayStyle() const {
+    return WebKit::WebScrollbar::ScrollbarOverlayStyleDefault;
+}
+bool PinchZoomScrollbar::isCustomScrollbar() const {
+    return false;
+}
+
+WebKit::WebScrollbar::Orientation PinchZoomScrollbar::orientation() const {
+    return orientation_;
+}
+
+}  // namespace cc