Add chrome.usbPrivate API for use by USB device WEBUI.

device/usb/usb_service_unittest.cc

Index: device/usb/usb_service_unittest.cc
diff --git a/device/usb/usb_service_unittest.cc b/device/usb/usb_service_unittest.cc
index 79a5bb74925bb89f91df221758006a78a5aa7466..1f8b8e2c36606fb5a010ed15d8c7d43119df1e04 100644
--- a/device/usb/usb_service_unittest.cc
+++ b/device/usb/usb_service_unittest.cc
@@ -32,9 +32,22 @@ TEST_F(UsbServiceTest, ClaimGadget) {
   ASSERT_TRUE(gadget.get());
 
   scoped_refptr<UsbDeviceHandle> handle = gadget->GetDevice()->Open();
-  base::string16 serial_utf16;
-  ASSERT_TRUE(handle->GetSerial(&serial_utf16));
-  ASSERT_EQ(gadget->GetSerial(), base::UTF16ToUTF8(serial_utf16));
+
+  base::string16 utf16;
+  ASSERT_TRUE(handle->GetManufacturer(&utf16));
+  ASSERT_EQ("Google Inc.", base::UTF16ToUTF8(utf16));
+  // Check again to make sure string descriptor caching works.
+  ASSERT_EQ("Google Inc.", base::UTF16ToUTF8(utf16));
+
+  ASSERT_TRUE(handle->GetProduct(&utf16));
+  ASSERT_EQ("Test Gadget (default state)", base::UTF16ToUTF8(utf16));
+  // Check again to make sure string descriptor caching works.
+  ASSERT_EQ("Test Gadget (default state)", base::UTF16ToUTF8(utf16));
+
+  ASSERT_TRUE(handle->GetSerial(&utf16));
+  ASSERT_EQ(gadget->GetSerial(), base::UTF16ToUTF8(utf16));
+  // Check again to make sure string descriptor caching works.
+  ASSERT_EQ(gadget->GetSerial(), base::UTF16ToUTF8(utf16));
 }
 
 TEST_F(UsbServiceTest, DisconnectAndReconnect) {