native/request: type fixes/changes

- Asset.{Title,Img,Video,Data} now use corresponding object types (ptr)
- Data.Len is uint64 now
- Image.{W,WMin,H,HMin} are uint64 now
- removed video.linearity from native fixture

native/request/asset.go

@@ -50,7 +50,7 @@ type Asset struct {
 	// Description:
 	//   Title object for title assets.
 	//   See TitleObject definition.
-	Title interface{} `json:"title,omitempty"`
+	Title *Title `json:"title,omitempty"`
 
 	// Field:
 	//   img
@@ -61,7 +61,7 @@ type Asset struct {
 	// Description:
 	//   Image object for image assets.
 	//   See ImageObject definition.
-	Img interface{} `json:"img,omitempty"`
+	Img *Image `json:"img,omitempty"`
 
 	// Field:
 	//   video
@@ -72,7 +72,7 @@ type Asset struct {
 	//   See the Video request object definition.
 	//   Note that in-stream (ie preroll, etc) video ads are not part of Native.
 	//   Native ads may contain a video as the ad creative itself.
-	Video interface{} `json:"video,omitempty"`
+	Video *Video `json:"video,omitempty"`
 
 	// Field:
 	//   data
@@ -83,7 +83,7 @@ type Asset struct {
 	// Description:
 	//   Data object for brand name, description, ratings, prices etc.
 	//   See DataObject definition.
-	Data interface{} `json:"data,omitempty"`
+	Data *Data `json:"data,omitempty"`
 
 	// Field:
 	//   ext

native/request/data.go

@@ -27,7 +27,7 @@ type Data struct {
 	//   integer
 	// Description:
 	//   Maximum length of the text in the element’s response.
-	Len int64 `json:"len,omitempty"`
+	Len uint64 `json:"len,omitempty"`
 
 	// Field:
 	//   ext

native/request/image.go

@@ -26,7 +26,7 @@ type Image struct {
 	//   integer
 	// Description:
 	//   Width of the image in pixels.
-	W int64 `json:"w,omitempty"`
+	W uint64 `json:"w,omitempty"`
 
 	// Field:
 	//   wmin
@@ -39,7 +39,7 @@ type Image struct {
 	//   This option should be used for any rescaling of images by the client.
 	//   Either w or wmin should be transmitted.
 	//   If only w is included, it should be considered an exact requirement.
-	WMin int64 `json:"wmin,omitempty"`
+	WMin uint64 `json:"wmin,omitempty"`
 
 	// Field:
 	//   h
@@ -49,7 +49,7 @@ type Image struct {
 	//   integer
 	// Description:
 	//   Height of the image in pixels.
-	H int64 `json:"h,omitempty"`
+	H uint64 `json:"h,omitempty"`
 
 	// Field:
 	//   hmin
@@ -62,7 +62,7 @@ type Image struct {
 	// This option should be used for any rescaling of images by the client.
 	// Either h or hmin should be transmitted.
 	// If only h is included, it should be considered an exact requirement.
-	HMin int64 `json:"hmin,omitempty"`
+	HMin uint64 `json:"hmin,omitempty"`
 
 	// Field:
 	//   mimes

native/request/testdata/content-context.json

@@ -8,7 +8,6 @@
 		{
 			"id": 4,
 			"video": {
-				"linearity": 1,
 				"minduration": 15,
 				"maxduration": 30,
 				"protocols": [