Put the Pepper stuff in the content namespace.

content/renderer/pepper/pepper_platform_context_3d_impl.h

Index: content/renderer/pepper/pepper_platform_context_3d_impl.h
diff --git a/content/renderer/pepper/pepper_platform_context_3d_impl.h b/content/renderer/pepper/pepper_platform_context_3d_impl.h
index 9180d4004ecc3136481e50a54b9945d9a4a78581..59fa85ecb4f1a4210340847fcb5e41a9b31b83f0 100644
--- a/content/renderer/pepper/pepper_platform_context_3d_impl.h
+++ b/content/renderer/pepper/pepper_platform_context_3d_impl.h
@@ -22,9 +22,12 @@ class CommandBuffer;
 
 class CommandBufferProxy;
 class GpuChannelHost;
-class PepperParentContextProvider;
 class ContentGLContext;
 
+namespace content {
+
+class PepperParentContextProvider;
+
 class PlatformContext3DImpl
     : public webkit::ppapi::PluginDelegate::PlatformContext3D {
  public:
@@ -59,6 +62,8 @@ class PlatformContext3DImpl
   base::WeakPtrFactory<PlatformContext3DImpl> weak_ptr_factory_;
 };
 
+}  // namespace content
+
 #endif  // ENABLE_GPU
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_PLATFORM_CONTEXT_3D_IMPL_H_