Introduce interface for memory dumps

tests/TraceMemoryDumpTest.cpp

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkTraceMemoryDump.h"
+
+#include "Test.h"
+
+/*
+ * Build test for SkTraceMemoryDump.
+ */
+class TestSkTraceMemoryDump : public SkTraceMemoryDump {
+public:
+    TestSkTraceMemoryDump() { }
+    ~TestSkTraceMemoryDump() override { }
+
+    void dumpScalarValue(const char* dumpName, const char* valueName, const char* units,
+                         uint64_t value) override { }
+    void setMemoryBacking(const char* dumpName, const char* backingType,
+                          const char* backingObjectId) override { }
+    void setDiscardableMemoryBacking(
+        const char* dumpName,
+        const SkDiscardableMemory& discardableMemoryObject) override { }
+};
+
+DEF_TEST(SkTraceMemoryDump, reporter) {
+    TestSkTraceMemoryDump x;
+    x.dumpScalarValue("foobar", "size", "bytes", 42);
+}