Fixes issues when switching between software and compositing.

content/renderer/browser_plugin/browser_plugin.cc

Index: content/renderer/browser_plugin/browser_plugin.cc
diff --git a/content/renderer/browser_plugin/browser_plugin.cc b/content/renderer/browser_plugin/browser_plugin.cc
index 59dd401f0a35291ac49ba5256ff6e37ff394a896..2370ec58060554fddcb7abe515639a62087d844a 100644
--- a/content/renderer/browser_plugin/browser_plugin.cc
+++ b/content/renderer/browser_plugin/browser_plugin.cc
@@ -817,9 +817,9 @@ void BrowserPlugin::EnableCompositing(bool enable) {
     return;
 
   if (enable && !compositing_helper_) {
-    compositing_helper_.reset(new BrowserPluginCompositingHelper(
+    compositing_helper_ = new BrowserPluginCompositingHelper(
         container_,
-        render_view_routing_id_));
+        render_view_routing_id_);
   }
 
   compositing_helper_->EnableCompositing(enable);
@@ -830,7 +830,8 @@ void BrowserPlugin::destroy() {
   // The BrowserPlugin's WebPluginContainer is deleted immediately after this
   // call returns, so let's not keep a reference to it around.
   container_ = NULL;
-  compositing_helper_.reset();
+  if (compositing_helper_)
+    compositing_helper_->OnContainerDestroy();
   MessageLoop::current()->DeleteSoon(FROM_HERE, this);
 }