* Electron version: 1.6.3
* Operating system: macOS 10.12.3 (Sierra)

### Expected behavior

`clipboard.read("com.adobe.pdf", "binary")` should return data as a `Buffer` or `String` with `binary` encoding if given clipboard data type is present.

### Actual behavior

Data is returned as `String`. When save to as a file using 'binary' encoding, file length is shorter than actual clipboard data size (verified using ClipboardViewer).

### How to reproduce

Use Sketch.app to draw a circle vector. Copy the circle into clipboard. One of the data types added to clipboard will be of type "com.adobe.pdf". Switch to test electron app that calls `clipboard.read`.
Now save the string to a file using `binary` encoding. Resulting PDF file can't be viewed as PDF and PDF validation will fail.

**UPDATE:** Other vector editing apps like Illustrator or Affinity Designer should also create `com.adobe.pdf" as well as Apple PDF Pasteboard type since this is how vector copy-paste works across editors.

**UPDATE2:** Just found a closed issue mentioning this may be due to Chromium returning only string. If this is true perhaps platform clipboard should be accessed directly instead of relying on Chromium.
atom/common/api/atom_api_clipboard.h
#ifndef ATOM_COMMON_API_ATOM_API_CLIPBOARD_H_
#define ATOM_COMMON_API_ATOM_API_CLIPBOARD_H_
#include <string>
#include <vector>
#include "native_mate/arguments.h"
#include "native_mate/dictionary.h"
#include "ui/base/clipboard/clipboard.h"
#include "ui/gfx/image/image.h"
namespace atom {
namespace api {
class Clipboard {