Add infrastructure for a USB device blocklist.

chrome/browser/usb/usb_blocklist.h

Index: chrome/browser/usb/usb_blocklist.h
diff --git a/chrome/browser/usb/usb_blocklist.h b/chrome/browser/usb/usb_blocklist.h
new file mode 100644
index 0000000000000000000000000000000000000000..4a444f95a20f0a3ee1966692e40a51ab7a5a43e2
--- /dev/null
+++ b/chrome/browser/usb/usb_blocklist.h
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_USB_USB_BLOCKLIST_H_
+#define CHROME_BROWSER_USB_USB_BLOCKLIST_H_
+
+#include <stdint.h>
+
+#include <set>
+
+#include "base/lazy_instance.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/strings/string_piece.h"
+
+namespace device {
+class UsbDevice;
+}
+
+class UsbBlocklist final {
+ public:
+  // An entry in the blocklist. Represents a specific version of a device that
+  // should not be accessible. These fields correspond to the idVendor,
+  // idProduct and bcdDevice fields of the device's USB device descriptor.
+  struct Entry {
+    Entry(uint16_t vendor_id, uint16_t product_id, uint16_t version);
+
+    uint16_t vendor_id;
+    uint16_t product_id;
+    uint16_t version;
+  };
+
+  ~UsbBlocklist();
+
+  // Returns a singleton instance of the blocklist.
+  static UsbBlocklist& Get();
+
+  // Adds a device to the blocklist to be excluded from access.
+  void Exclude(const Entry&);
+
+  // Adds a device to the blocklist by parsing a blocklist string and calling
+  // Exclude(entry).
+  //
+  // The blocklist string must be a comma-separated list of
+  // idVendor:idProduct:bcdDevice triples, where each member of the triple is a
+  // 16-bit integer written as exactly 4 hexadecimal digits. The triples may
+  // be separated by whitespace. Triple components are colon-separated and must
+  // not have whitespace around the colon.
+  //
+  // Invalid entries in the comma-separated list will be ignored.
+  //
+  // Example:
+  //   "1000:001C:0100, 1000:001D:0101, 123:ignored:0"
+  void Exclude(base::StringPiece blocklist_string);
+
+  // Returns if a device is excluded from access.
+  bool IsExcluded(const Entry&);
+  bool IsExcluded(scoped_refptr<const device::UsbDevice>);
+
+  // Size of the blocklist.
+  size_t size() { return blocklisted_devices_.size(); }
+
+  // Reload the blocklist for testing purposes.
+  void ResetToDefaultValuesForTest();
+
+ private:
+  // friend LazyInstance to permit access to private constructor.
+  friend base::DefaultLazyInstanceTraits<UsbBlocklist>;
+
+  UsbBlocklist();
+
+  void PopulateWithDefaultValues();
+
+  // Populates the blocklist with values obtained dynamically from a server,
+  // able to be updated without shipping new executable versions.
+  void PopulateWithServerProvidedValues();
+
+  // Set of blocklist entries.
+  std::set<Entry> blocklisted_devices_;
+
+  DISALLOW_COPY_AND_ASSIGN(UsbBlocklist);
+};
+
+#endif  // CHROME_BROWSER_USB_USB_BLOCKLIST_H_