Loading screenshots and simple 1-to-1 comparison of screenshots

chrome/browser/chromeos/login/screenshot_tester.h

Index: chrome/browser/chromeos/login/screenshot_tester.h
diff --git a/chrome/browser/chromeos/login/screenshot_tester.h b/chrome/browser/chromeos/login/screenshot_tester.h
index 5a1d05226d58a82bb08ef50a182f39e57ee6b2b0..d9319e83ccf0cf1bdaca73e6a7e0e3bd85f32c4d 100644
--- a/chrome/browser/chromeos/login/screenshot_tester.h
+++ b/chrome/browser/chromeos/login/screenshot_tester.h
@@ -5,6 +5,8 @@
 #ifndef CHROME_BROWSER_CHROMEOS_LOGIN_SCREENSHOT_TESTER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_SCREENSHOT_TESTER_H_
 
+#include <string>
+
 #include "base/base_export.h"
 #include "base/bind_internal.h"
 #include "base/files/file_path.h"
@@ -29,34 +31,56 @@ class ScreenshotTester {
 
   // Does all the work that has been stated through switches:
   // updates golden screenshot or takes a new screenshot and compares it
-  // with the golden one (this part is not implemented yet).
-  void Run(const std::string& file_name);
+  // with the golden one. |test_name| is the name of the test from which
+  // we run this method.
+  void Run(const std::string& test_name);
 
  private:
   typedef scoped_refptr<base::RefCountedBytes> PNGFile;
 
-  // Takes a screenshot and puts it to |screenshot_| field.
-  void TakeScreenshot();
+  // Takes a screenshot and returns it.
+  PNGFile TakeScreenshot();
+
+  // Saves |png_data| as a new golden screenshot for test |test_name_|.
+  void UpdateGoldenScreenshot(PNGFile png_data);
 
-  // Saves |png_data| as a new golden screenshot for this test.
-  void UpdateGoldenScreenshot(const std::string& file_name, PNGFile png_data);
+  // Saves an image |png_data|, assuming it is a .png file.
+  // Returns true if image was saved successfully.
+  bool SaveImage(const std::string& file_name,
+                 const base::FilePath& screenshot_dir,
+                 PNGFile png_data);
 
   // Saves |png_data| as a current screenshot.
-  void ReturnScreenshot(PNGFile png_data);
+  void ReturnScreenshot(const PNGFile& screenshot, PNGFile png_data);
+
+  // Loads golden screenshot from the disk. Fails if there is no
+  // golden screenshot for test |test_name_|.
+  PNGFile LoadGoldenScreenshot();
+
+  // Compares two given screenshots and saves |sample|
+  // and difference between |sample| and |model|, if they differ in any pixel.
+  void CompareScreenshots(PNGFile model, PNGFile sample);
+
+  // Name of the test from which Run() method has been called.
+  // Used for generating names for screenshot files.
+  std::string test_name_;
 
   // Path to the directory for golden screenshots.
-  base::FilePath screenshot_dest_;
+  base::FilePath golden_screenshots_dir_;
+
+  // Path to the directory where screenshots that failed comparing
+  // and difference between them and golden ones will be stored.
+  base::FilePath artifacts_dir_;
 
   // |run_loop_| and |run_loop_quitter_| are used to synchronize
   // with ui::GrabWindowSnapshotAsync.
   base::RunLoop run_loop_;
   base::Closure run_loop_quitter_;
 
-  // Current screenshot.
-  PNGFile screenshot_;
+  // Is true when we're in test mode:
+  // comparing golden screenshots and current ones.
+  bool test_mode_;
 
-  // Is true when we running updating golden screenshots mode.
-  bool update_golden_screenshot_;
   base::WeakPtrFactory<ScreenshotTester> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenshotTester);