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

third_party/WebKit/Source/web/WebLocalFrameImpl.cpp

Index: third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp b/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
index eb7bedf9e8492582942cbe4242a0bf950248b1c3..71dfa1bfd5d63040bb9503701165f9f5fb59c9c7 100644
--- a/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
+++ b/third_party/WebKit/Source/web/WebLocalFrameImpl.cpp
@@ -1975,6 +1975,17 @@ void WebLocalFrameImpl::didFail(const ResourceError& error, bool wasProvisional,
         client()->didFailProvisionalLoad(this, webError, webCommitType);
     else
         client()->didFailLoad(this, webError, webCommitType);
+    if (WebPluginContainerImpl* plugin = pluginContainerFromFrame(frame()))
+        plugin->didFailLoading(error);
+}
+
+void WebLocalFrameImpl::didFinish()
+{
+    if (!client())
+        return;
+    client()->didFinishLoad(this);
+    if (WebPluginContainerImpl* plugin = pluginContainerFromFrame(frame()))
+        plugin->didFinishLoading();
 }
 
 void WebLocalFrameImpl::setCanHaveScrollbars(bool canHaveScrollbars)