Revert CL 117933003. Re-add resource speculative prefetching code.

chrome/browser/predictors/resource_prefetch_predictor_tab_helper.h

+// Copyright 2014 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 CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TAB_HELPER_H_
+#define CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TAB_HELPER_H_
+
+#include "content/public/browser/web_contents_observer.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+namespace predictors {
+
+class ResourcePrefetchPredictorTabHelper
+    : public content::WebContentsObserver,
+      public content::WebContentsUserData<ResourcePrefetchPredictorTabHelper> {
+ public:
+  virtual ~ResourcePrefetchPredictorTabHelper();
+
+  // content::WebContentsObserver implementation
+  virtual void DocumentOnLoadCompletedInMainFrame() OVERRIDE;
+  virtual void DidLoadResourceFromMemoryCache(
+      const content::LoadFromMemoryCacheDetails& details) OVERRIDE;
+
+ private:
+  explicit ResourcePrefetchPredictorTabHelper(
+      content::WebContents* web_contents);
+  friend class content::WebContentsUserData<ResourcePrefetchPredictorTabHelper>;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourcePrefetchPredictorTabHelper);
+};
+
+}  // namespace predictors
+
+#endif  // CHROME_BROWSER_PREDICTORS_RESOURCE_PREFETCH_PREDICTOR_TAB_HELPER_H_