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

content/common/child_trace_message_filter.h

Index: content/common/child_trace_message_filter.h
===================================================================
--- content/common/child_trace_message_filter.h	(revision 163290)
+++ content/common/child_trace_message_filter.h	(working copy)
@@ -11,6 +11,8 @@
 #include "base/process.h"
 #include "ipc/ipc_channel_proxy.h"
 
+namespace content {
+
 // This class sends and receives trace messages on child processes.
 class ChildTraceMessageFilter : public IPC::ChannelProxy::MessageFilter {
  public:
@@ -44,6 +46,6 @@
   DISALLOW_COPY_AND_ASSIGN(ChildTraceMessageFilter);
 };
 
+}  // namespace content
 
 #endif  // CONTENT_COMMON_CHILD_TRACE_MESSAGE_FILTER_H_
-