Add an UMA histogram for WebUSB function calls.

third_party/WebKit/Source/core/frame/UseCounter.h

Index: third_party/WebKit/Source/core/frame/UseCounter.h
diff --git a/third_party/WebKit/Source/core/frame/UseCounter.h b/third_party/WebKit/Source/core/frame/UseCounter.h
index 63594354e989e889ef2f878b7ca6ecc373742742..ec14e880f387701a23a0a9e36b4818e901b5ec3d 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1289,6 +1289,22 @@ public:
         NavigatorPointerEnabled = 1516,
         InputSelectionGettersThrow = 1517,
         DocumentCreateEventVRDisplayEvent = 1518,
+        UsbGetDevices = 1519,
+        UsbRequestDevice = 1520,
+        UsbDeviceOpen = 1521,
+        UsbDeviceClose = 1522,
+        UsbDeviceSelectConfiguration = 1523,
+        UsbDeviceClaimInterface = 1524,
+        UsbDeviceReleaseInterface = 1525,
+        UsbDeviceSelectAlternateInterface = 1526,
+        UsbDeviceControlTransferIn = 1527,
+        UsbDeviceControlTransferOut = 1528,
+        UsbDeviceClearHalt = 1529,
+        UsbDeviceTransferIn = 1530,
+        UsbDeviceTransferOut = 1531,
+        UsbDeviceIsochronousTransferIn = 1532,
+        UsbDeviceIsochronousTransferOut = 1533,
+        UsbDeviceReset = 1534,
 
         // Add new features immediately above this line. Don't change assigned
         // numbers of any item, and don't reuse removed slots.