Rework UMAHistogramHelper and StatisticsDeltaReader into [Chrome]HistogramTester.

content/public/test/browser_test_utils.h

 // Copyright (c) 2012 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_PUBLIC_TEST_BROWSER_TEST_UTILS_H_
 #define CONTENT_PUBLIC_TEST_BROWSER_TEST_UTILS_H_
 
 #include <queue>
 #include <string>
 #include <vector>
@@ skipping 170 matching lines @@
                               const std::vector<int>& js_resource_ids);
 
 // Returns the cookies for the given url.
 std::string GetCookies(BrowserContext* browser_context, const GURL& url);
 
 // Sets a cookie for the given url. Returns true on success.
 bool SetCookie(BrowserContext* browser_context,
                const GURL& url,
                const std::string& value);
 
+// Fetch the histograms data from other processes. This should be called after
+// the test code has been executed but before performing assertions.
+void FetchHistogramsFromChildProcesses();
+
 // Watches title changes on a WebContents, blocking until an expected title is
 // set.
 class TitleWatcher : public WebContentsObserver {
  public:
   // |web_contents| must be non-NULL and needs to stay alive for the
   // entire lifetime of |this|. |expected_title| is the title that |this|
   // will wait for.
   TitleWatcher(WebContents* web_contents,
                const base::string16& expected_title);
   virtual ~TitleWatcher();
@@ skipping 99 matching lines @@
   NotificationRegistrar registrar_;
   std::queue<std::string> message_queue_;
   scoped_refptr<MessageLoopRunner> message_loop_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(DOMMessageQueue);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_BROWSER_TEST_UTILS_H_