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 9730bb95ffc54a7c5c825f6c812c0aa1c51013f0..9716b9cf4651d51c1d235dc0365c0f3007c74540 100644
--- a/content/renderer/pepper/pepper_platform_context_3d_impl.h
+++ b/content/renderer/pepper/pepper_platform_context_3d_impl.h
@@ -21,9 +21,12 @@ class CommandBuffer;
 
 class CommandBufferProxy;
 class GpuChannelHost;
-class PepperParentContextProvider;
 class ContentGLContext;
 
+namespace content {
+
+class PepperParentContextProvider;
+
 class PlatformContext3DImpl
     : public webkit::ppapi::PluginDelegate::PlatformContext3D {
  public:
@@ -58,6 +61,8 @@ class PlatformContext3DImpl
   base::WeakPtrFactory<PlatformContext3DImpl> weak_ptr_factory_;
 };
 
+}  // namespace content
+
 #endif  // ENABLE_GPU
 
 #endif  // CONTENT_RENDERER_PEPPER_PEPPER_PLATFORM_CONTEXT_3D_IMPL_H_