Revert of [DevTools] Implement DevToolsManager::Observer which notifies about target updates.

content/browser/devtools/render_view_devtools_agent_host.cc

Index: content/browser/devtools/render_view_devtools_agent_host.cc
diff --git a/content/browser/devtools/render_view_devtools_agent_host.cc b/content/browser/devtools/render_view_devtools_agent_host.cc
index 62355fae4b7c50b3ae2430046e84c25548c612d2..3da9a23524f71939758431d1f2c57f9887a3ee1f 100644
--- a/content/browser/devtools/render_view_devtools_agent_host.cc
+++ b/content/browser/devtools/render_view_devtools_agent_host.cc
@@ -130,7 +130,6 @@
   power_handler_->SetNotifier(notifier);
   g_instances.Get().push_back(this);
   AddRef();  // Balanced in RenderViewHostDestroyed.
-  DevToolsManager::GetInstance()->AgentHostChanged(this);
 }
 
 WebContents* RenderViewDevToolsAgentHost::GetWebContents() {
@@ -300,7 +299,6 @@
   scoped_refptr<RenderViewDevToolsAgentHost> protect(this);
   HostClosed();
   ClearRenderViewHost();
-  DevToolsManager::GetInstance()->AgentHostChanged(this);
   Release();
 }
 
@@ -350,16 +348,6 @@
   overrides_handler_->DidDetachInterstitialPage();
 }
 
-void RenderViewDevToolsAgentHost::TitleWasSet(
-    NavigationEntry* entry, bool explicit_set) {
-  DevToolsManager::GetInstance()->AgentHostChanged(this);
-}
-
-void RenderViewDevToolsAgentHost::NavigationEntryCommitted(
-    const LoadCommittedDetails& load_details) {
-  DevToolsManager::GetInstance()->AgentHostChanged(this);
-}
-
 void RenderViewDevToolsAgentHost::Observe(int type,
                                           const NotificationSource& source,
                                           const NotificationDetails& details) {