Make scroll offset type of float in cc

cc/trees/layer_tree_host_common.cc

Index: cc/trees/layer_tree_host_common.cc
diff --git a/cc/trees/layer_tree_host_common.cc b/cc/trees/layer_tree_host_common.cc
index 8d25539725914ee4d495f5ac580b86ae70aec0d4..624fe6b07a8cec5d30686bb3111f6b5d46da4efb 100644
--- a/cc/trees/layer_tree_host_common.cc
+++ b/cc/trees/layer_tree_host_common.cc
@@ -52,13 +52,13 @@ static gfx::Vector2dF GetEffectiveScrollDelta(LayerType* layer) {
 }
 
 template <typename LayerType>
-static gfx::Vector2dF GetEffectiveTotalScrollOffset(LayerType* layer) {
-  gfx::Vector2dF offset = layer->TotalScrollOffset();
+static gfx::ScrollOffset GetEffectiveTotalScrollOffset(LayerType* layer) {
+  gfx::ScrollOffset offset = layer->TotalScrollOffset();
   // The scroll parent's total scroll offset (scroll offset + scroll delta)
   // can't be used because its scroll offset has already been applied to the
   // scroll children's positions by the main thread layer positioning code.
   if (layer->scroll_parent())
-    offset += layer->scroll_parent()->ScrollDelta();
+    offset += gfx::ScrollOffset(layer->scroll_parent()->ScrollDelta());
   return offset;
 }
 
@@ -1645,8 +1645,8 @@ static void CalculateDrawPropertiesInternal(
         layer->parent()->screen_space_transform_is_animating();
   }
   gfx::Point3F transform_origin = layer->transform_origin();
-  gfx::Vector2dF scroll_offset = GetEffectiveTotalScrollOffset(layer);
-  gfx::PointF position = layer->position() - scroll_offset;
+  gfx::ScrollOffset scroll_offset = GetEffectiveTotalScrollOffset(layer);
+  gfx::PointF position = layer->position() - scroll_offset.ToVector2dF();
   gfx::Transform combined_transform = data_from_ancestor.parent_matrix;
   if (!layer->transform().IsIdentity()) {
     // LT = Tr[origin] * Tr[origin2transformOrigin]