When running DM, write test failures to json.

dm/DMTestTask.h

 #ifndef DMTestTask_DEFINED
 #define DMTestTask_DEFINED
 
 #include "DMReporter.h"
+#include "DMJsonWriter.h"
 #include "DMTask.h"
 #include "DMTaskRunner.h"
 #include "SkString.h"
 #include "SkTemplates.h"
 #include "Test.h"
 
 // Runs a unit test.
 namespace DM {
 
 class TestReporter : public skiatest::Reporter {
 public:
   TestReporter() {}
 
   const char* failure() const { return fFailure.c_str(); }
 
 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;
+      failure.getFailureString(&newFailure);
+      // TODO: Better to store an array of failures?
+      if (!fFailure.isEmpty()) {
+          fFailure.append("\n\t\t");
+      }
+      fFailure.append(newFailure);
   }
 
   SkString fFailure;
 };
 
 class CpuTestTask : public CpuTask {
 public:
     CpuTestTask(Reporter*, TaskRunner*, skiatest::TestRegistry::Factory);
 
     virtual void draw() SK_OVERRIDE;
@@ skipping 16 matching lines @@
 
 private:
     TestReporter fTestReporter;
     SkAutoTDelete<skiatest::Test> fTest;
     const SkString fName;
 };
 
 }  // namespace DM
 
 #endif // DMTestTask_DEFINED