fix skpdiff viewer bug when using relative paths

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 146 matching lines @@
     DiffRecord* currentRecord = fRecords;
     if (useJSONP) {
         stream.writeText("var SkPDiffRecords = {\n");
     } else {
         stream.writeText("{\n");
     }
     stream.writeText("    \"records\": [\n");
     while (NULL != currentRecord) {
         stream.writeText("        {\n");
 
+            char* baselineAbsPath = get_absolute_path(currentRecord->fBaselinePath.c_str());
+            char* testAbsPath = get_absolute_path(currentRecord->fTestPath.c_str());
+
             stream.writeText("            \"baselinePath\": \"");
-            stream.writeText(currentRecord->fBaselinePath.c_str());
+            stream.writeText(baselineAbsPath);
             stream.writeText("\",\n");
 
             stream.writeText("            \"testPath\": \"");
-            stream.writeText(currentRecord->fTestPath.c_str());
+            stream.writeText(testAbsPath);
             stream.writeText("\",\n");
 
+            free(baselineAbsPath);
+            free(testAbsPath);
+
             stream.writeText("            \"diffs\": [\n");
             for (int diffIndex = 0; diffIndex < currentRecord->fDiffs.count(); diffIndex++) {
                 DiffData& data = currentRecord->fDiffs[diffIndex];
                 stream.writeText("                {\n");
 
                     stream.writeText("                    \"differName\": \"");
                     stream.writeText(data.fDiffName);
                     stream.writeText("\",\n");
 
                     stream.writeText("                    \"result\": ");
@@ skipping 96 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;
     }
 }