Make scroll offset type of float in cc

cc/blink/web_layer_impl.cc

Index: cc/blink/web_layer_impl.cc
diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index c1f67fbed3af08fbe712b402c8c9e47b58a24ddb..3a89208e35d8789ec6919e71958b56ab30c7320b 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -27,6 +27,7 @@
 #include "third_party/WebKit/public/platform/WebLayerScrollClient.h"
 #include "third_party/WebKit/public/platform/WebSize.h"
 #include "third_party/skia/include/utils/SkMatrix44.h"
+#include "ui/gfx/geometry/vector2d_conversions.h"
 
 using cc::Animation;
 using cc::Layer;
@@ -267,12 +268,23 @@ void WebLayerImpl::setForceRenderSurface(bool force_render_surface) {
   layer_->SetForceRenderSurface(force_render_surface);
 }
 
+void WebLayerImpl::setScrollPositionFloat(
+    const std::pair<double, double>& position) {

[danakj, 2014/09/25 15:13:30]

are you allowed to use std::pair in the blink public API? i guess you'll sort
that out on that side of the fence

[Yufeng Shen (Slow to review), 2014/09/25 20:06:23]

right, it is suggested to use a new type WebDoublePoint.

I will sync this patch with the patch that adds this new type
to blink side.

+  layer_->SetScrollOffset(gfx::ScrollOffset(position.first, position.second));
+}
+
+std::pair<double, double> WebLayerImpl::scrollPositionFloat() const {
+  return std::pair<double, double>(layer_->scroll_offset().x(),
+                                   layer_->scroll_offset().y());
+}
+
 void WebLayerImpl::setScrollPosition(blink::WebPoint position) {
-  layer_->SetScrollOffset(gfx::Point(position).OffsetFromOrigin());
+  layer_->SetScrollOffset(gfx::ScrollOffset(position.x, position.y));
 }
 
 blink::WebPoint WebLayerImpl::scrollPosition() const {
-  return gfx::PointAtOffsetFromOrigin(layer_->scroll_offset());
+  return gfx::PointAtOffsetFromOrigin(
+      gfx::ToFlooredVector2d(layer_->scroll_offset()));
 }
 
 void WebLayerImpl::setScrollClipLayer(WebLayer* clip_layer) {