Create stub GrAuditTrail class

include/gpu/GrContext.h

Index: include/gpu/GrContext.h
diff --git a/include/gpu/GrContext.h b/include/gpu/GrContext.h
index 39477e0db81fbdc0875aec82f4220664336be11f..a49d141810cc857441df5ad19162589b1235b567 100644
--- a/include/gpu/GrContext.h
+++ b/include/gpu/GrContext.h
@@ -17,6 +17,7 @@
 #include "SkMatrix.h"
 #include "SkPathEffect.h"
 #include "SkTypes.h"
+#include "../private/GrAuditTrail.h"
 #include "../private/GrSingleOwner.h"
 #include "../private/SkMutex.h"
 
@@ -358,6 +359,8 @@ public:
     /** Get pointer to atlas texture for given mask format */
     GrTexture* getFontAtlasTexture(GrMaskFormat format);
 
+    SkString dumpAuditTrailToJson() const { return fAuditTrail.toJson(); }
+
 private:
     GrGpu*                          fGpu;
     const GrCaps*                   fCaps;
@@ -405,6 +408,8 @@ private:
 
     SkAutoTDelete<GrDrawingManager> fDrawingManager;
 
+    GrAuditTrail                    fAuditTrail;
+
     // TODO: have the CMM use drawContexts and rm this friending
     friend class GrClipMaskManager; // the CMM is friended just so it can call 'drawingManager'
     friend class GrDrawingManager;  // for access to drawingManager for ProgramUnitTest