When running DM, write test failures to json.

tests/skia_test.cpp

Index: tests/skia_test.cpp
diff --git a/tests/skia_test.cpp b/tests/skia_test.cpp
index 172328ee4abf1d44bd9414e9917b71c86fb6edf7..6d72ed0761b1d79fb7c8737bd69cdfee351bb48a 100644
--- a/tests/skia_test.cpp
+++ b/tests/skia_test.cpp
@@ -58,7 +58,9 @@ public:
     virtual bool verbose()           const SK_OVERRIDE { return FLAGS_veryVerbose; }
 
 protected:
-    virtual void onReportFailed(const SkString& desc) SK_OVERRIDE {
+    virtual void onReportFailed(const skiatest::Failure& failure) SK_OVERRIDE {
+        SkString desc;
+        skiatest::Failure::GetFailureString(&desc, failure);
         SkDebugf("\nFAILED: %s", desc.c_str());
     }