Add RAPPOR metric recording for Device{Orientation,Motion} in blink.

Source/modules/device_orientation/DeviceMotionController.cpp

Index: Source/modules/device_orientation/DeviceMotionController.cpp
diff --git a/Source/modules/device_orientation/DeviceMotionController.cpp b/Source/modules/device_orientation/DeviceMotionController.cpp
index adb45324a4dc2e939c7c0bd77bef3d0247749600..8e546f46e046174439c0a255ee5949db350cdc7d 100644
--- a/Source/modules/device_orientation/DeviceMotionController.cpp
+++ b/Source/modules/device_orientation/DeviceMotionController.cpp
@@ -13,6 +13,7 @@
 #include "modules/device_orientation/DeviceMotionDispatcher.h"
 #include "modules/device_orientation/DeviceMotionEvent.h"
 #include "platform/weborigin/SecurityOrigin.h"
+#include "public/platform/Platform.h"
 
 namespace blink {
 
@@ -59,6 +60,9 @@ void DeviceMotionController::didAddEventListener(LocalDOMWindow* window, const A
         }
     }
 
+    if (!m_hasEventListener)
+        Platform::current()->recordRapporMetric(WebPlatformEventDeviceMotion, WebURL(document().url()));
+
     DeviceSingleWindowEventController::didAddEventListener(window, eventType);
 }