Oilpan: tidy up finalization of InspectorEmulationAgent following r192106.

Source/web/InspectorEmulationAgent.cpp

Index: Source/web/InspectorEmulationAgent.cpp
diff --git a/Source/web/InspectorEmulationAgent.cpp b/Source/web/InspectorEmulationAgent.cpp
index 4d0895ca6af78f7ac25129de600118cc3661bcaf..d27751e2b01409a4ac6e6e58d74ccf34317e0236 100644
--- a/Source/web/InspectorEmulationAgent.cpp
+++ b/Source/web/InspectorEmulationAgent.cpp
@@ -36,7 +36,6 @@ InspectorEmulationAgent::InspectorEmulationAgent(WebViewImpl* webViewImpl)
 
 InspectorEmulationAgent::~InspectorEmulationAgent()
 {
-    m_webViewImpl->devToolsEmulator()->setEmulationAgent(nullptr);
 }
 
 void InspectorEmulationAgent::restore()
@@ -55,6 +54,11 @@ void InspectorEmulationAgent::disable(ErrorString*)
     setEmulatedMedia(&error, String());
 }
 
+void InspectorEmulationAgent::discardAgent()
+{
+    m_webViewImpl->devToolsEmulator()->setEmulationAgent(nullptr);
+}
+
 void InspectorEmulationAgent::didCommitLoadForLocalFrame(LocalFrame* frame)
 {
     if (frame == m_webViewImpl->mainFrameImpl()->frame())