[Sensors] Add an UMA histogram for Generic Sensor 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 8f30b7646468427160bae39d0a451ca3edba9672..e789186fbbf58b6387d9fb455729b394aec0ecc2 100644
--- a/third_party/WebKit/Source/core/frame/UseCounter.h
+++ b/third_party/WebKit/Source/core/frame/UseCounter.h
@@ -1387,6 +1387,8 @@ class CORE_EXPORT UseCounter {
     RTCSessionDescriptionInitNoType = 1677,
     RTCSessionDescriptionInitNoSdp = 1678,
     HTMLMediaElementPreloadForcedMetadata = 1679,
+    GenericSensorStart = 1680,
+    GenericSensorStop = 1681,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.