winaura: Do not create WindowObservers for BrowserPlugin.

content/browser/web_contents/web_contents_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 1201 matching lines @@
     // explicitly add this WebContentsViewAura to their tree after they create
     // us.
     if (root_window) {
       aura::client::ParentWindowWithContext(
           window_.get(), root_window, root_window->GetBoundsInScreen());
     }
   }
   window_->layer()->SetMasksToBounds(true);
   window_->SetName("WebContentsViewAura");
 
-  window_observer_.reset(new WindowObserver(this));
+  // WindowObserver is not interesting and is problematic for Browser Plugin
+  // guests.
+  // The use cases for WindowObserver do not apply to Browser Plugins:
+  // 1) guests do not support NPAPI plugins.
+  // 2) guests' window bounds are supposed to come from its embedder.
+  if (!web_contents_->GetRenderProcessHost()->IsGuest())
+    window_observer_.reset(new WindowObserver(this));
 
   // delegate_->GetDragDestDelegate() creates a new delegate on every call.
   // Hence, we save a reference to it locally. Similar model is used on other
   // platforms as well.
   if (delegate_)
     drag_dest_delegate_ = delegate_->GetDragDestDelegate();
 }
 
 RenderWidgetHostView* WebContentsViewAura::CreateViewForWidget(
     RenderWidgetHost* render_widget_host) {
@@ skipping 465 matching lines @@
       event.location(),
       gfx::Screen::GetScreenFor(GetNativeView())->GetCursorScreenPoint(),
       ConvertAuraEventFlagsToWebInputEventModifiers(event.flags()));
   if (drag_dest_delegate_)
     drag_dest_delegate_->OnDrop();
   current_drop_data_.reset();
   return current_drag_op_;
 }
 
 }  // namespace content