fix skpdiff viewer bug when using relative paths

tools/skpdiff/SkDiffContext.cpp

Index: tools/skpdiff/SkDiffContext.cpp
diff --git a/tools/skpdiff/SkDiffContext.cpp b/tools/skpdiff/SkDiffContext.cpp
index cf2654ac054ca395933e84d677f7f146b9cd5deb..07e2a0bb880ba688ec517ad4e6633c450a654d23 100644
--- a/tools/skpdiff/SkDiffContext.cpp
+++ b/tools/skpdiff/SkDiffContext.cpp
@@ -164,14 +164,20 @@ void SkDiffContext::outputRecords(SkWStream& stream, bool useJSONP) {
     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];