content/browser: Move more files into the content namespace.

content/browser/trace_message_filter.cc

Index: content/browser/trace_message_filter.cc
diff --git a/content/browser/trace_message_filter.cc b/content/browser/trace_message_filter.cc
index 17dbee7926d5b6d5139dba1a60459b9aa538ff4c..17c9cb0039e87777fa0a6037480ba69e4ba3fa66 100644
--- a/content/browser/trace_message_filter.cc
+++ b/content/browser/trace_message_filter.cc
@@ -7,14 +7,12 @@
 #include "content/browser/trace_controller_impl.h"
 #include "content/common/child_process_messages.h"
 
-using content::BrowserMessageFilter;
-using content::BrowserThread;
-using content::TraceControllerImpl;
-
-TraceMessageFilter::TraceMessageFilter() :
-    has_child_(false),
-    is_awaiting_end_ack_(false),
-    is_awaiting_buffer_percent_full_ack_(false) {
+namespace content {
+
+TraceMessageFilter::TraceMessageFilter()
+    : has_child_(false),
+      is_awaiting_end_ack_(false),
+      is_awaiting_buffer_percent_full_ack_(false) {
 }
 
 void TraceMessageFilter::OnFilterAdded(IPC::Channel* channel) {
@@ -126,3 +124,4 @@ void TraceMessageFilter::OnTraceBufferPercentFullReply(float percent_full) {
   }
 }
 
+}  // namespace content