Factor DRP PreviewsState logic out of content

components/data_reduction_proxy/content/renderer/BUILD.gn

+# Copyright 2017 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.
+
+static_library("renderer") {
+  sources = [
+    "content_previews_render_frame_observer.cc",
+    "content_previews_render_frame_observer.h",
+  ]
+  deps = [
+    "//base",
+    "//components/data_reduction_proxy/core/common",
+    "//content/public/common",
+    "//content/public/renderer",
+    "//third_party/WebKit/public:blink",
+  ]
+}
+
+source_set("unit_tests") {
+  testonly = true
+  sources = [
+    "content_previews_render_frame_observer_unittest.cc",
+  ]
+  deps = [
+    ":renderer",
+    "//base/test:test_support",
+    "//content/public/common",
+    "//testing/gtest",
+    "//third_party/WebKit/public:blink",
+  ]
+}