Modify skpdiff to write diffs directly to provided directories

tools/skpdiff/SkDiffContext.h

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkDiffContext_DEFINED
 #define SkDiffContext_DEFINED
 
@@ skipping 34 matching lines @@
 
     /**
      * Sets the directory within which to store whiteDiffs (images showing white
      * for each pixel that differs between baseline and test).
      *
      * If the directory does not exist yet, it will be created.
      */
     void setWhiteDiffDir(const SkString& directory);
 
     /**
+     * Modify the pattern used to generate commonName (= the 
+     * basename of rgb/white diff files).
+     *
+     * - true: basename is a combination of the input file names.
+     * - false: basename is the common prefix of the input file names.
+     *
+     * For example, for:
+     *   baselinePath=/tmp/dir/image-before.png
+     *   testPath=/tmp/dir/image-after.png
+     * 
+     * If setLongNames(true), commonName would be:
+     *    image-before-png-vs-image-after-png.png
+     * 
+     * If setLongNames(false), commonName would be:
+     *   image-.png
+     */
+    void setLongNames(const bool useLongNames);
+
+    /**
      * Sets the differs to be used in each diff. Already started diffs will not retroactively use
      * these.
      * @param differs An array of differs to use. The array is copied, but not the differs
      *                themselves.
      */
     void setDiffers(const SkTDArray<SkImageDiffer*>& differs);
 
     /**
      * Compares two directories of images with the given differ
      * @param baselinePath The baseline directory's path
@@ skipping 13 matching lines @@
      * @param baselinePath The baseline file path
      * @param testPath     The matching test file path
      */
     void addDiff(const char* baselinePath, const char* testPath);
 
     /**
      * Output the records of each diff in JSON.
      *
      * The format of the JSON document is one top level array named "records".
      * Each record in the array is an object with the following values:
-     *    "commonName"     : string containing the common prefix of the baselinePath
-     *                       and testPath filenames
+     *    "commonName"     : string containing the output filename (basename) 
+     *                       depending on the value of 'longNames'. 
+     *                       (see 'setLongNames' for an explanation and example).
      *    "baselinePath"   : string containing the path to the baseline image
      *    "testPath"       : string containing the path to the test image
      *    "differencePath" : (optional) string containing the path to an alpha
      *                       mask of the pixel difference between the baseline
      *                       and test images
      *                       TODO(epoger): consider renaming this "alphaMaskPath"
      *                       to distinguish from other difference types?
      *    "rgbDiffPath"    : (optional) string containing the path to a bitmap
      *                       showing per-channel differences between the
      *                       baseline and test images at each pixel
@@ skipping 70 matching lines @@
     // results.
     SkTLList<DiffRecord> fRecords;
 
     SkImageDiffer** fDiffers;
     int fDifferCount;
     int fThreadCount;
 
     SkString fAlphaMaskDir;
     SkString fRgbDiffDir;
     SkString fWhiteDiffDir;
+    bool longNames;
 };
 
 #endif