**Do you want to request a *feature* or report a *bug*?** 

Report a bug.

**What is the current behavior?**

Whenever I render SVG elements that are camel cased (e.g. `<linearGradient />`) on the server side,  I get the following warning:

```
Warning: <linearGradient /> is using uppercase HTML. Always use lowercase HTML tags in React.
```

**What is the expected behavior?**

Warnings should be consistent with the client side rendering, if possible. In this case, I'd expect no warning, since using camel cased SVG element names is pretty standard.

For client side rendering, there seems to be a check for the current namespace:

https://github.com/facebook/react/blob/efcac24af26afba90e2ef525509ca40f3bd6f270/src/renderers/dom/fiber/ReactDOMFiberComponent.js#L344-L352

For server side rendering, there seems to be currently no such check in place:

https://github.com/facebook/react/blob/81706eeb7a51c1cea7fd8e66733a4f4618155ef5/src/renderers/shared/server/ReactPartialRenderer.js#L537-L544

**Which versions of React, and which browser / OS are affected by this issue? Did this work in previous versions of React?**

Hitting this on 16.0.0-beta.5. Was not hitting it on 15.6.1, the version I was previously on.

Thanks in advance.
var ReactInputSelection = require('ReactInputSelection');
var ReactInstanceMap = require('ReactInstanceMap');
var ReactPortal = require('ReactPortal');
var ReactVersion = require('ReactVersion');
var {isValidElement} = require('react');
var {injectInternals} = require('ReactFiberDevToolsHook');
var {
  ELEMENT_NODE,
  TEXT_NODE,
  COMMENT_NODE,
  DOCUMENT_NODE,
  DOCUMENT_FRAGMENT_NODE,
} = require('HTMLNodeType');
var {ROOT_ATTRIBUTE_NAME} = require('DOMProperty');
var findDOMNode = require('findDOMNode');
var invariant = require('fbjs/lib/invariant');
var {
  createElement,
  getChildNamespace,
  setInitialProperties,
  diffProperties,
  updateProperties,
  diffHydratedProperties,
  diffHydratedText,
  warnForDeletedHydratableElement,
  warnForDeletedHydratableText,
  warnForInsertedHydratedElement,
  warnForInsertedHydratedText,
} = ReactDOMFiberComponent;
var {precacheFiberNode, updateFiberProps} = ReactDOMComponentTree;