Update skpdiff to include a name with each file.

tools/skpdiff/SkDiffContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkImageDecoder.h"
 #include "SkOSFile.h"
@@ skipping 149 matching lines @@
     } else {
         stream.writeText("{\n");
     }
     stream.writeText("    \"records\": [\n");
     while (NULL != currentRecord) {
         stream.writeText("        {\n");
 
             SkString baselineAbsPath = get_absolute_path(currentRecord->fBaselinePath);
             SkString testAbsPath = get_absolute_path(currentRecord->fTestPath);
 
+            // strip off directory structure and find the common part of the filename
+            SkString baseName = SkOSPath::SkBasename(baselineAbsPath.c_str());
+            SkString testName = SkOSPath::SkBasename(testAbsPath.c_str());
+            for (size_t x = 0; x < baseName.size(); ++x) {
+                if (baseName[x] != testName[x]) {
+                    baseName.insertUnichar(x, '\n');
+                    break;
+                }
+            }
+
+            stream.writeText("            \"commonName\": \"");
+            stream.writeText(baseName.c_str());
+            stream.writeText("\",\n");
+
             stream.writeText("            \"baselinePath\": \"");
             stream.writeText(baselineAbsPath.c_str());
             stream.writeText("\",\n");
 
             stream.writeText("            \"testPath\": \"");
             stream.writeText(testAbsPath.c_str());
             stream.writeText("\",\n");
 
             stream.writeText("            \"diffs\": [\n");
             for (int diffIndex = 0; diffIndex < currentRecord->fDiffs.count(); diffIndex++) {
@@ skipping 104 matching lines @@
         for (int i = 0; i < cntColumns; i++) {
             SkString str;
             str.printf(", %f", values[i]);
             stream.writeText(str.c_str());
         }
         stream.writeText("\n");
 
         currentRecord = currentRecord->fNext;
     }
 }