Make blink::JSONValue (and subclasses) use unique_ptr rather than RefPtrs.

third_party/WebKit/Source/platform/graphics/LoggingCanvas.h

Index: third_party/WebKit/Source/platform/graphics/LoggingCanvas.h
diff --git a/third_party/WebKit/Source/platform/graphics/LoggingCanvas.h b/third_party/WebKit/Source/platform/graphics/LoggingCanvas.h
index 1d2f0bceb32d4681b4f0bb73f27007e80b71d6dd..1bf9661fb3193bf531c017dd8f073ccb40af4e8c 100644
--- a/third_party/WebKit/Source/platform/graphics/LoggingCanvas.h
+++ b/third_party/WebKit/Source/platform/graphics/LoggingCanvas.h
@@ -33,13 +33,17 @@
 
 #include "platform/JSONValues.h"
 #include "platform/graphics/InterceptingCanvas.h"
+#include <memory>
 
 namespace blink {
 
 class LoggingCanvas : public InterceptingCanvasBase {
 public:
     LoggingCanvas(int width, int height);
-    PassRefPtr<JSONArray> log();
+
+    // Gives the caller ownership of the current log data, and clears the log
+    // for future operations.
+    std::unique_ptr<JSONArray> log();
 
     void onDrawPaint(const SkPaint&) override;
     void onDrawPoints(PointMode, size_t count, const SkPoint pts[], const SkPaint&) override;
@@ -75,7 +79,7 @@ public:
 private:
     friend class AutoLogger;
 
-    RefPtr<JSONArray> m_log;
+    std::unique_ptr<JSONArray> m_log;
 };
 
 #ifndef NDEBUG