Move content_shell and content_browsertests code into the content namespace.

content/shell/shell_main.cc

Index: content/shell/shell_main.cc
===================================================================
--- content/shell/shell_main.cc	(revision 147404)
+++ content/shell/shell_main.cc	(working copy)
@@ -20,7 +20,7 @@
 int APIENTRY wWinMain(HINSTANCE instance, HINSTANCE, wchar_t*, int) {
   sandbox::SandboxInterfaceInfo sandbox_info = {0};
   content::InitializeSandboxInfo(&sandbox_info);
-  ShellMainDelegate delegate;
+  content::ShellMainDelegate delegate;
   return content::ContentMain(instance, &sandbox_info, &delegate);
 }
 
@@ -32,7 +32,7 @@
   // delegate types.
   return ::ContentMain(argc, argv);
 #else
-  ShellMainDelegate delegate;
+  content::ShellMainDelegate delegate;
   return content::ContentMain(argc, argv, &delegate);
 #endif  // OS_MACOSX
 }