Oilpan: tidy up finalization of InspectorEmulationAgent following r192106.

Source/web/InspectorEmulationAgent.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "web/InspectorEmulationAgent.h"
 
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/Settings.h"
@@ skipping 18 matching lines @@
 
 InspectorEmulationAgent::InspectorEmulationAgent(WebViewImpl* webViewImpl)
     : InspectorBaseAgent<InspectorEmulationAgent, InspectorFrontend::Emulation>("Emulation")
     , m_webViewImpl(webViewImpl)
 {
     m_webViewImpl->devToolsEmulator()->setEmulationAgent(this);
 }
 
 InspectorEmulationAgent::~InspectorEmulationAgent()
 {
-    m_webViewImpl->devToolsEmulator()->setEmulationAgent(nullptr);
 }
 
 void InspectorEmulationAgent::restore()
 {
     ErrorString error;
     setScriptExecutionDisabled(&error, m_state->getBoolean(EmulationAgentState::scriptExecutionDisabled));
     setTouchEmulationEnabled(&error, m_state->getBoolean(EmulationAgentState::touchEventEmulationEnabled), nullptr);
     setEmulatedMedia(&error, m_state->getString(EmulationAgentState::emulatedMedia));
 }
 
 void InspectorEmulationAgent::disable(ErrorString*)
 {
     ErrorString error;
     setScriptExecutionDisabled(&error, false);
     setTouchEmulationEnabled(&error, false, nullptr);
     setEmulatedMedia(&error, String());
 }
 
+void InspectorEmulationAgent::discardAgent()
+{
+    m_webViewImpl->devToolsEmulator()->setEmulationAgent(nullptr);
+}
+
 void InspectorEmulationAgent::didCommitLoadForLocalFrame(LocalFrame* frame)
 {
     if (frame == m_webViewImpl->mainFrameImpl()->frame())
         viewportChanged();
 }
 
 void InspectorEmulationAgent::resetScrollAndPageScaleFactor(ErrorString*)
 {
     m_webViewImpl->resetScrollAndScaleState();
 }
@@ skipping 45 matching lines @@
         .setMaximumPageScaleFactor(m_webViewImpl->maximumPageScaleFactor());
     frontend()->viewportChanged(viewport);
 }
 
 DEFINE_TRACE(InspectorEmulationAgent)
 {
     InspectorBaseAgent::trace(visitor);
 }
 
 } // namespace blink