Receive all messages in PluginObserver from the RenderFrameHost.

BUG=444203

Review URL: https://codereview.chromium.org/1063413002

Cr-Commit-Position: refs/heads/master@{#324407}

chrome/browser/plugins/plugin_observer.cc

@@ -336,17 +336,6 @@ bool PluginObserver::OnMessageReceived(
   IPC_BEGIN_MESSAGE_MAP(PluginObserver, message)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_BlockedOutdatedPlugin,
                         OnBlockedOutdatedPlugin)
-    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_NPAPINotSupported,
-                        OnNPAPINotSupported)
-
-    IPC_MESSAGE_UNHANDLED(return false)
-  IPC_END_MESSAGE_MAP()
-
-  return true;
-}
-
-bool PluginObserver::OnMessageReceived(const IPC::Message& message) {
-  IPC_BEGIN_MESSAGE_MAP(PluginObserver, message)
 #if defined(ENABLE_PLUGIN_INSTALLATION)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_RemovePluginPlaceholderHost,
                         OnRemovePluginPlaceholderHost)
@@ -355,6 +344,8 @@ bool PluginObserver::OnMessageReceived(const IPC::Message& message) {
                         OnOpenAboutPlugins)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_CouldNotLoadPlugin,
                         OnCouldNotLoadPlugin)
+    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_NPAPINotSupported,
+                        OnNPAPINotSupported)
 
     IPC_MESSAGE_UNHANDLED(return false)
   IPC_END_MESSAGE_MAP()

chrome/browser/plugins/plugin_observer.h

@@ -42,7 +42,6 @@ class PluginObserver : public content::WebContentsObserver,
                      base::ProcessId plugin_pid) override;
   bool OnMessageReceived(const IPC::Message& message,
                          content::RenderFrameHost* render_frame_host) override;
-  bool OnMessageReceived(const IPC::Message& message) override;
 
  private:
   explicit PluginObserver(content::WebContents* web_contents);