document arguments for webview methods

docs/api/webview-tag.md

@@ -537,20 +537,42 @@ Stops any `findInPage` request for the `webview` with the provided `action`.
 
 ### `<webview>.print([options])`
 
+* `options` Object (optional)
+  * `silent` Boolean - Don't ask user for print settings. Default is `false`.
+  * `printBackground` Boolean - Also prints the background color and image of
+    the web page. Default is `false`.
+
 Prints `webview`'s web page. Same as `webContents.print([options])`.
 
 ### `<webview>.printToPDF(options, callback)`
 
+* `options` Object
+  * `marginsType` Integer - (optional) Specifies the type of margins to use. Uses 0 for
+    default margin, 1 for no margin, and 2 for minimum margin.
+  * `pageSize` String - (optional) Specify page size of the generated PDF. Can be `A3`,
+    `A4`, `A5`, `Legal`, `Letter`, `Tabloid` or an Object containing `height`
+    and `width` in microns.
+  * `printBackground` Boolean - (optional) Whether to print CSS backgrounds.
+  * `printSelectionOnly` Boolean - (optional) Whether to print selection only.
+  * `landscape` Boolean - (optional) `true` for landscape, `false` for portrait.
+* `callback` Function
+  * `error` Error
+  * `data` Buffer
+
 Prints `webview`'s web page as PDF, Same as `webContents.printToPDF(options, callback)`.
 
 ### `<webview>.capturePage([rect, ]callback)`
 
+* `rect` [Rectangle](structures/rectangle.md) (optional) - The area of the page to be captured
+* `callback` Function
+  * `image` [NativeImage](native-image.md)
+
 Captures a snapshot of the `webview`'s page. Same as `webContents.capturePage([rect, ]callback)`.
 
 ### `<webview>.send(channel[, arg1][, arg2][, ...])`
 
 * `channel` String
-* `arg` (optional)
+* `...args` any[]
 
 Send an asynchronous message to renderer process via `channel`, you can also
 send arbitrary arguments. The renderer process can handle the message by