Move a bunch of code in content\common (as well as a few left in renderer) to the content namespace.

content/common/webmessageportchannel_impl.h

Index: content/common/webmessageportchannel_impl.h
===================================================================
--- content/common/webmessageportchannel_impl.h	(revision 163290)
+++ content/common/webmessageportchannel_impl.h	(working copy)
@@ -15,6 +15,8 @@
 #include "ipc/ipc_listener.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebMessagePortChannel.h"
 
+namespace content {
+
 // This is thread safe.
 class WebMessagePortChannelImpl
     : public WebKit::WebMessagePortChannel,
@@ -74,4 +76,6 @@
   DISALLOW_COPY_AND_ASSIGN(WebMessagePortChannelImpl);
 };
 
+}  // namespace content
+
 #endif  // CONTENT_COMMON_WEBMESSAGEPORTCHANNEL_IMPL_H_