Add a couple of linux-specific exports for the content component build.

content/browser/plugin_loader_posix.h

Index: content/browser/plugin_loader_posix.h
diff --git a/content/browser/plugin_loader_posix.h b/content/browser/plugin_loader_posix.h
index 1af295799eabe21e4cfd56de7a04065f250c4c42..97fe8bb5355c43bac3b7f6ff780e6b3e75031aaa 100644
--- a/content/browser/plugin_loader_posix.h
+++ b/content/browser/plugin_loader_posix.h
@@ -42,8 +42,8 @@ class MessageLoopProxy;
 // 5. This algorithm continues until the canonical list has been walked to the
 //    end, after which the list of loaded plugins is set on the PluginList and
 //    the completion callback is run.
-class PluginLoaderPosix : public UtilityProcessHost::Client,
-                                 IPC::Message::Sender {
+class CONTENT_EXPORT PluginLoaderPosix : public UtilityProcessHost::Client,
+                                                IPC::Message::Sender {
  public:
   PluginLoaderPosix();