Makes RenderFrameObserver/RenderViewObserver::OnDestruct pure virtual.

content/renderer/devtools/devtools_client.cc

Index: content/renderer/devtools/devtools_client.cc
diff --git a/content/renderer/devtools/devtools_client.cc b/content/renderer/devtools/devtools_client.cc
index 3f9612938248ba0dffbf37410fdb090d88c1f9cd..edc31a3f368000e9f1a39e592d4084a0801b2eb9 100644
--- a/content/renderer/devtools/devtools_client.cc
+++ b/content/renderer/devtools/devtools_client.cc
@@ -39,6 +39,10 @@ void DevToolsClient::DidClearWindowObject() {
     render_frame()->ExecuteJavaScript(base::UTF8ToUTF16(compatibility_script_));
 }
 
+void DevToolsClient::OnDestruct() {
+  delete this;
+}
+
 void DevToolsClient::sendMessageToEmbedder(const WebString& message) {
   Send(new DevToolsHostMsg_DispatchOnEmbedder(routing_id(),
                                               message.utf8()));