BatteryManager: release promise resolver once resolved.

Source/modules/battery/BatteryManager.cpp

Index: Source/modules/battery/BatteryManager.cpp
diff --git a/Source/modules/battery/BatteryManager.cpp b/Source/modules/battery/BatteryManager.cpp
index a100fe59d4725c5a192a58003ca75cce92b25f1a..57cfa22ae62565d02832a0bc39f8f6625ef52e19 100644
--- a/Source/modules/battery/BatteryManager.cpp
+++ b/Source/modules/battery/BatteryManager.cpp
@@ -44,6 +44,7 @@ ScriptPromise BatteryManager::startRequest(ScriptState* scriptState)
     if (m_state == Resolved) {
         // FIXME: Consider returning the same promise in this case. See crbug.com/385025.
         m_resolver->resolve(this);
+        m_resolver = nullptr;
     } else if (m_state == NotStarted) {
         m_state = Pending;
         m_hasEventListener = true;
@@ -85,6 +86,7 @@ void BatteryManager::didUpdateData()
         ASSERT(m_resolver);
         m_state = Resolved;
         m_resolver->resolve(this);
+        m_resolver = nullptr;
         return;
     }