Introduce interface for memory dumps

src/core/SkTraceMemoryDump.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkTraceMemoryDump_DEFINED
+#define SkTraceMemoryDump_DEFINED
+
+#include "SkTypes.h"
+
+class SkDiscardableMemory;
+class SkString;
+
+/**
+ * Interface for memory tracing.
+ * This interface is meant to be passed as argument to the memory dump methods
+ * of Skia objects. The implementation of this interface is provided by the
+ * embedder.
+ *
+ * const char* argument values are assumed to have long-lived scope and will not
+ * be copied.
+ */
+class SK_API SkTraceMemoryDump {
+public:
+  /**

[ericrk, 2015/08/19 12:45:28]

skia uses 4 space indent.

[Primiano Tucci (use gerrit), 2015/08/20 08:48:01]

Ah, I guess I was relying too much on clang-format :)

+   *  Appends a new memory dump (i.e. a row) to the trace memory infrastructure.
+   *  If dumpName does not exist yet, a new one is created. Otherwise, a new
+   *  column is appended to the previously created dump.
+   *  Arguements:
+   *    dumpName: an absolute, slash-separated, name for the item being dumped
+   *        e.g., "skia/CacheX/EntryY"
+   *    name: a string indicating the name of the column.
+   *        e.g., "size", "active_size", "number_of_objects".
+   *    units: a string indicating the units for the scalar.
+   *        e.g., "bytes", "objects".
+   *    value: the actual value being dumped.
+   */
+  virtual void DumpScalarValue(const SkString &dumpName, const char *name,

[ericrk, 2015/08/19 12:45:28]

Skia uses different coding style - lowercase for member fns I believe
(dumpScalarValue)?

[Primiano Tucci (use gerrit), 2015/08/20 08:48:01]

Done.

+                               const char *units, uint64_t value) = 0;
+
+  /**
+   * Sets the memory backing for an existing dump.
+   * backingType and backingObjectId are used by the embedder to associate
+   * the memory dumped via DumpScalarValue with the corresponding dump that
+   * backs the memory.
+   */
+  virtual void SetMemoryBacking(const SkString &dumpName,

[ericrk, 2015/08/19 12:45:28]

* and & appear to bind left in skia - "const SkString& dumpName"

[Primiano Tucci (use gerrit), 2015/08/20 08:48:01]

Done.

+                                const SkString &backingType,
+                                const SkString &backingObjectId) = 0;
+
+  /**
+   * Specialization for memory backed by discardable memory.
+   */
+  virtual void SetDiscardableMemoryBacking(
+      const SkString &dumpName,
+      const SkDiscardableMemory &discardableMemoryObject) = 0;
+
+protected:
+  virtual ~SkTraceMemoryDump() = 0;

[ericrk, 2015/08/19 12:45:28]

{}? Other cases (SkDiscardable) appear to inline this.

[Primiano Tucci (use gerrit), 2015/08/20 08:48:01]

Done.

+};
+
+#endif