Move a bunch of content\common code into the content namespace.

content/common/gpu/gpu_surface_lookup.h

Index: content/common/gpu/gpu_surface_lookup.h
===================================================================
--- content/common/gpu/gpu_surface_lookup.h	(revision 163460)
+++ content/common/gpu/gpu_surface_lookup.h	(working copy)
@@ -7,6 +7,8 @@
 
 #include "ui/gfx/native_widget_types.h"
 
+namespace content {
+
 // This class provides an interface to look up window surface handles
 // that cannot be sent through the IPC channel.
 class GpuSurfaceLookup {
@@ -23,4 +25,6 @@
   DISALLOW_COPY_AND_ASSIGN(GpuSurfaceLookup);
 };
 
+}  // namespace content
+
 #endif  // CONTENT_COMMON_GPU_GPU_SURFACE_LOOKUP_H_