Add getUserSelectedDevices to the USB extensions API.

extensions/browser/api/extensions_api_client.h

Index: extensions/browser/api/extensions_api_client.h
diff --git a/extensions/browser/api/extensions_api_client.h b/extensions/browser/api/extensions_api_client.h
index 9cf4d9722ee8b3b9f8985f78febbb4962b3b13a7..0ce8eb8755f7ac98bbd91bb1424eeeb77454c507 100644
--- a/extensions/browser/api/extensions_api_client.h
+++ b/extensions/browser/api/extensions_api_client.h
@@ -98,6 +98,10 @@ class ExtensionsAPIClient {
       content::BrowserContext* browser_context,
       RulesCacheDelegate* cache_delegate) const;
 
+  // Creates a DevicePermissionsPrompt appropriate for the embedder.
+  virtual scoped_ptr<DevicePermissionsPrompt> CreateDevicePermissionsPrompt(
+      content::WebContents* web_contents) const;
+
   // NOTE: If this interface gains too many methods (perhaps more than 20) it
   // should be split into one interface per API.
 };