Create stub GrAuditTrail class

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1572553002

Review URL: https://codereview.chromium.org/1572553002

gyp/gpu.gypi

@@ -55,8 +55,10 @@
       '<(skia_include_path)/gpu/gl/GrGLTypes.h',
 
       # Private includes
+      '<(skia_include_path)/private/GrAuditTrail.h',
       '<(skia_include_path)/private/GrSingleOwner.h',
 
+      '<(skia_src_path)/gpu/GrAuditTrail.cpp',
       '<(skia_src_path)/gpu/GrAutoLocaleSetter.h',
       '<(skia_src_path)/gpu/GrAllocator.h',
       '<(skia_src_path)/gpu/GrBatchAtlas.cpp',

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

include/private/GrAuditTrail.h

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrAuditTrail_DEFINED
+#define GrAuditTrail_DEFINED
+
+#include "SkString.h"
+#include "SkTArray.h"
+
+/*
+ * GrAuditTrail collects a list of draw ops, detailed information about those ops, and can dump them
+ * to json.
+ */
+class GrAuditTrail {
+public:
+    void addOp(SkString name) {
+        fOps.push_back().fName = name;
+    }
+
+    SkString toJson() const;
+
+    void reset() { fOps.reset(); }
+
+private:
+    struct Op {
+        SkString toJson() const;
+        SkString fName;
+    };
+
+    SkTArray<Op> fOps;
+};
+
+#endif

src/gpu/GrAuditTrail.cpp

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrAuditTrail.h"
+
+SkString GrAuditTrail::toJson() const {
+    SkString json;
+    json.append("{\n");
+    json.append("Ops: [\n");
+    for (int i = 0; i < fOps.count(); i++) {
+        json.append(fOps[i].toJson());
+        if (i < fOps.count() - 1) {
+            json.append(",\n");
+        }
+    }
+    json.append("]\n");
+    json.append("}\n");
+    return json;
+}
+
+SkString GrAuditTrail::Op::toJson() const {
+    SkString json;
+    json.append("{\n");
+    json.appendf("%s\n", fName.c_str());
+    json.append("}\n");
+    return json;
+}
+