content: Delete webkit_support.h

This file was just a placeholder, including blink_test_environment.h
waiting for Blink to be updated.

Now that Blink was updated and rolled into Chromium, we can remove it.

Chromium side (part 1) ->
https://src.chromium.org/viewvc/chrome?revision=288636&view=revision
Blink side (part 2) ->
https://src.chromium.org/viewvc/blink?revision=179977&view=revision
Chromium side (part 3) -> this patch

BUG=None
TEST=webkit_unit_tests
R=avi@chromium.org

Review URL: https://codereview.chromium.org/463603003

Cr-Commit-Position: refs/heads/master@{#289200}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289200 0039d316-1c4b-4281-b951-d872f2087c98

content/test/webkit_support.h

-// Copyright 2013 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef CONTENT_TEST_WEBKIT_SUPPORT_H_
-#define CONTENT_TEST_WEBKIT_SUPPORT_H_
-
-// TODO(tfarina): Remove this file when Blink is changed to include
-// blink_test_environment.h
-#include "content/test/blink_test_environment.h"
-
-#endif  // CONTENT_TEST_WEBKIT_SUPPORT_H_