Add path utils, plus a test for it.

gm/gm_expectations.cpp

Index: gm/gm_expectations.cpp
diff --git a/gm/gm_expectations.cpp b/gm/gm_expectations.cpp
index 71311d5e116d6fa7c923352b9e3f3576f5fb0124..0188e756f4406e121b3499dc9861cee5a9065a88 100644
--- a/gm/gm_expectations.cpp
+++ b/gm/gm_expectations.cpp
@@ -34,15 +34,6 @@ namespace skiagm {
         va_end(args);
     }
 
-    SkString SkPathJoin(const char *rootPath, const char *relativePath) {
-        SkString result(rootPath);
-        if (!result.endsWith(SkPATH_SEPARATOR)) {
-            result.appendUnichar(SkPATH_SEPARATOR);
-        }
-        result.append(relativePath);
-        return result;
-    }
-
     // TODO(epoger): This currently assumes that the result SkHashDigest was
     // generated as an SkHashDigest of an SkBitmap.  We'll need to allow for other
     // hash types to cover non-bitmaps.
@@ -160,7 +151,7 @@ namespace skiagm {
     // IndividualImageExpectationsSource class...
 
     Expectations IndividualImageExpectationsSource::get(const char *testName) {
-        SkString path = SkPathJoin(fRootDir.c_str(), testName);
+        SkString path = SkOSPathUtils::SkPathJoin(fRootDir.c_str(), testName);
         SkBitmap referenceBitmap;
         bool decodedReferenceBitmap =
             SkImageDecoder::DecodeFile(path.c_str(), &referenceBitmap,