Add a section to Site Settings listing USB devices.

chrome/android/java/src/org/chromium/chrome/browser/preferences/website/UsbInfo.java

 // 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.
 
 package org.chromium.chrome.browser.preferences.website;
 
 import java.io.Serializable;
 
 /**
  * USB device information for a given origin.
+ *
+ * These objects are compared only by the identity of the device, not by which site has permission
+ * to access it.
  */
 public class UsbInfo implements Serializable {
     private final String mOrigin;
     private final String mEmbedder;
     private final String mName;
     private final String mObject;
 
     UsbInfo(String origin, String embedder, String name, String object) {
         mOrigin = origin;
         mEmbedder = embedder;
@@ skipping 21 matching lines @@
     public String getName() {
         return mName;
     }
 
     /**
      * Revokes permission for the origin to access the USB device.
      */
     public void revoke() {
         WebsitePreferenceBridge.nativeRevokeUsbPermission(mOrigin, mEmbedder, mObject);
     }
+
+    @Override
+    public int hashCode() {
+        return mObject.hashCode();

[Ted C, 2016/08/15 20:31:59]

I find this to be somewhat odd.

Why not just expose mObject and use that for the key in your maps?  This just
seems like you are special casing this behavior to one implementation in the UI
and that seems fragile.

If we keep this as is, I think we should write some simple tests that force this
behavior to be maintained as I don't think the comment above would be sufficient
for people to realize the implications of changing it.

[Reilly Grant (use Gerrit), 2016/08/16 17:41:59]

Good idea, done.

+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof UsbInfo) {
+            UsbInfo other = (UsbInfo) obj;
+            return mObject.equals(other.mObject);
+        }
+        return false;
+    }
 }