When running DM, write test failures to json.

dm/DMTestTask.h

Index: dm/DMTestTask.h
diff --git a/dm/DMTestTask.h b/dm/DMTestTask.h
index ceb0e12e968f6d251e7ce4f16a527eebf359dc55..709ed47b1abb489ef0271df74314586e659592b0 100644
--- a/dm/DMTestTask.h
+++ b/dm/DMTestTask.h
@@ -2,6 +2,7 @@
 #define DMTestTask_DEFINED
 
 #include "DMReporter.h"
+#include "DMJsonWriter.h"
 #include "DMTask.h"
 #include "DMTaskRunner.h"
 #include "SkString.h"
@@ -21,8 +22,15 @@ private:
   virtual bool allowExtendedTest() const SK_OVERRIDE;
   virtual bool verbose()           const SK_OVERRIDE;
 
-  virtual void onReportFailed(const SkString& desc) SK_OVERRIDE {
-      fFailure = desc;
+  virtual void onReportFailed(const skiatest::Failure& failure) SK_OVERRIDE {
+      JsonWriter::AddTestFailure(failure);
+
+      SkString newFailure;
+      skiatest::Failure::GetFailureString(&newFailure, failure);
+      if (!fFailure.isEmpty()) {
+          fFailure.append("\n\t\t");
+      }
+      fFailure.append(newFailure);

[scroggo, 2014/11/05 20:40:17]

This change in behavior is orthogonal to the rest of my change. Was it
deliberate that DM overwrites previous failures? Most of our tests include
multiple REPORTER_ASSERTs, and I think it is preferable to be able to see them
all.

[mtklein, 2014/11/06 15:24:05]

Nope.  This seems like a good change to me.  Might be better to store an
SkTArray<SkString> fFailures, but this seems like a good thing to land right
away.

[scroggo, 2014/11/06 16:52:32]

Yeah, I considered doing that, but I wasn't sure the best way to plumb it
through. If it's alright by you (and it sounds like it is), I'll leave that as a
TODO.

   }
 
   SkString fFailure;