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

content/app/content_main_runner.cc

Index: content/app/content_main_runner.cc
===================================================================
--- content/app/content_main_runner.cc	(revision 163290)
+++ content/app/content_main_runner.cc	(working copy)
@@ -91,8 +91,8 @@
 }
 #endif
 
+namespace content {
 extern int GpuMain(const content::MainFunctionParams&);
-namespace content {
 extern int PluginMain(const content::MainFunctionParams&);
 extern int PpapiPluginMain(const MainFunctionParams&);
 extern int PpapiBrokerMain(const MainFunctionParams&);