Move the following files to content\public\plugin.

content/content_plugin.gypi

Index: content/content_plugin.gypi
===================================================================
--- content/content_plugin.gypi	(revision 104808)
+++ content/content_plugin.gypi	(working copy)
@@ -14,11 +14,8 @@
   'sources': [
     # All .cc, .h, .m, and .mm files under plugins except for tests and
     # mocks.
-    'plugin/content_plugin_client.h',
     'plugin/plugin_channel.cc',
     'plugin/plugin_channel.h',
-    'plugin/plugin_interpose_util_mac.mm',
-    'plugin/plugin_interpose_util_mac.h',
     'plugin/plugin_main.cc',
     'plugin/plugin_main_linux.cc',
     'plugin/plugin_main_mac.mm',
@@ -30,6 +27,9 @@
     'plugin/webplugin_delegate_stub.h',
     'plugin/webplugin_proxy.cc',
     'plugin/webplugin_proxy.h',
+    'public/plugin/content_plugin_client.h',
+    'public/plugin/plugin_interpose_util_mac.h',
+    'public/plugin/plugin_interpose_util_mac.mm',
   ],
   # These are layered in conditionals in the event other platforms
   # end up using this module as well.