Separate JSON functions from DMWriteTask.

Add JsonWriter, which handles Json output from DM, in preparation for
adding json output for tests. This change should not affect behavior.

BUG=skia:2454

Review URL: https://codereview.chromium.org/702513003
diff --git a/dm/DMJsonWriter.cpp b/dm/DMJsonWriter.cpp
new file mode 100644
index 0000000..f862647
--- /dev/null
+++ b/dm/DMJsonWriter.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "DMJsonWriter.h"
+
+#include "SkCommonFlags.h"
+#include "SkJSONCPP.h"
+#include "SkOSFile.h"
+#include "SkStream.h"
+#include "SkTArray.h"
+#include "SkThread.h"
+
+namespace DM {
+
+SkTArray<JsonWriter::BitmapResult> gBitmapResults;
+SK_DECLARE_STATIC_MUTEX(gBitmapResultLock);
+
+void JsonWriter::AddBitmapResult(const BitmapResult& result) {
+    SkAutoMutexAcquire lock(&gBitmapResultLock);
+    gBitmapResults.push_back(result);
+}
+
+void JsonWriter::DumpJson() {
+    if (FLAGS_writePath.isEmpty()) {
+        return;
+    }
+
+    Json::Value root;
+
+    for (int i = 1; i < FLAGS_properties.count(); i += 2) {
+        root[FLAGS_properties[i-1]] = FLAGS_properties[i];
+    }
+    for (int i = 1; i < FLAGS_key.count(); i += 2) {
+        root["key"][FLAGS_key[i-1]] = FLAGS_key[i];
+    }
+
+    {
+        SkAutoMutexAcquire lock(&gBitmapResultLock);
+        for (int i = 0; i < gBitmapResults.count(); i++) {
+            Json::Value result;
+            result["key"]["name"]            = gBitmapResults[i].name.c_str();
+            result["key"]["config"]          = gBitmapResults[i].config.c_str();
+            result["key"]["mode"]            = gBitmapResults[i].mode.c_str();
+            result["options"]["source_type"] = gBitmapResults[i].sourceType.c_str();
+            result["md5"]                    = gBitmapResults[i].md5.c_str();
+
+            root["results"].append(result);
+        }
+    }
+
+    SkString path = SkOSPath::Join(FLAGS_writePath[0], "dm.json");
+    SkFILEWStream stream(path.c_str());
+    stream.writeText(Json::StyledWriter().write(root).c_str());
+    stream.flush();
+}
+
+} // namespace DM