bluetooth: Add usecounter for gattserverdisconnected

We are looking into changing gattserverdisconnected to
gattserverdisconnect.

Review-Url: https://codereview.chromium.org/2841293002
Cr-Commit-Position: refs/heads/master@{#467594}

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

@@ -1578,6 +1578,7 @@ class CORE_EXPORT UseCounter {
     kDispatchMouseEventOnDisabledFormControl = 1967,
     kElementNameDOMInvalidHTMLParserValid = 1968,
     kElementNameDOMValidHTMLParserInvalid = 1969,
+    kGATTServerDisconnectedEvent = 1970,
 
     // Add new features immediately above this line. Don't change assigned
     // numbers of any item, and don't reuse removed slots.

third_party/WebKit/Source/modules/bluetooth/BluetoothDevice.cpp

@@ -4,17 +4,19 @@
 
 #include "modules/bluetooth/BluetoothDevice.h"
 
+#include <memory>
+#include <utility>
+
 #include "bindings/core/v8/CallbackPromiseAdapter.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "core/dom/DOMException.h"
 #include "core/events/Event.h"
+#include "core/frame/UseCounter.h"
 #include "modules/bluetooth/Bluetooth.h"
 #include "modules/bluetooth/BluetoothAttributeInstanceMap.h"
 #include "modules/bluetooth/BluetoothError.h"
 #include "modules/bluetooth/BluetoothRemoteGATTServer.h"
-#include <memory>
-#include <utility>
 
 namespace blink {
 
@@ -96,4 +98,15 @@ DEFINE_TRACE(BluetoothDevice) {
   ContextLifecycleObserver::Trace(visitor);
 }
 
+void BluetoothDevice::AddedEventListener(
+    const AtomicString& event_type,
+    RegisteredEventListener& registered_listener) {
+  EventTargetWithInlineData::AddedEventListener(event_type,
+                                                registered_listener);
+  if (event_type == EventTypeNames::gattserverdisconnected) {
+    UseCounter::Count(GetExecutionContext(),
+                      UseCounter::kGATTServerDisconnectedEvent);
+  }
+}
+
 }  // namespace blink

third_party/WebKit/Source/modules/bluetooth/BluetoothDevice.h

@@ -91,6 +91,11 @@ class BluetoothDevice final : public EventTargetWithInlineData,
 
   DEFINE_ATTRIBUTE_EVENT_LISTENER(gattserverdisconnected);
 
+ protected:
+  // EventTarget overrides:
+  void AddedEventListener(const AtomicString& eventType,
+                          RegisteredEventListener&) override;
+
  private:
   // Holds all GATT Attributes associated with this BluetoothDevice.
   Member<BluetoothAttributeInstanceMap> attribute_instance_map_;

tools/metrics/histograms/histograms.xml

@@ -97386,6 +97386,7 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   <int value="1967" label="DispatchMouseEventOnDisabledFormControl"/>
   <int value="1968" label="ElementNameDOMInvalidHTMLParserValid"/>
   <int value="1969" label="ElementNameDOMValidHTMLParserInvalid"/>
+  <int value="1970" label="GATTServerDisconnectedEvent"/>
 </enum>
 
 <enum name="FetchRequestMode" type="int">