Remove PluginLoadObserver and related logic, it was only used for NPAPI.

content/plugin/plugin_channel.cc

Index: content/plugin/plugin_channel.cc
diff --git a/content/plugin/plugin_channel.cc b/content/plugin/plugin_channel.cc
index 219f2f155bb2153c695dbef09fffc3f8ddf80779..852d71a2b3888da6309fb584941eea64404e1a5d 100644
--- a/content/plugin/plugin_channel.cc
+++ b/content/plugin/plugin_channel.cc
@@ -253,7 +253,6 @@ bool PluginChannel::OnControlMessageReceived(const IPC::Message& msg) {
                                     OnDestroyInstance)
     IPC_MESSAGE_HANDLER(PluginMsg_GenerateRouteID, OnGenerateRouteID)
     IPC_MESSAGE_HANDLER(PluginProcessMsg_ClearSiteData, OnClearSiteData)
-    IPC_MESSAGE_HANDLER(PluginHostMsg_DidAbortLoading, OnDidAbortLoading)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   DCHECK(handled);
@@ -327,13 +326,4 @@ void PluginChannel::OnClearSiteData(const std::string& site,
   Send(new PluginProcessHostMsg_ClearSiteDataResult(success));
 }
 
-void PluginChannel::OnDidAbortLoading(int render_view_id) {
-  for (size_t i = 0; i < plugin_stubs_.size(); ++i) {
-    if (plugin_stubs_[i]->webplugin()->host_render_view_routing_id() ==
-            render_view_id) {
-      plugin_stubs_[i]->delegate()->instance()->CloseStreams();
-    }
-  }
-}
-
 }  // namespace content