Introduce interface for memory dumps

include/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;

[reed1, 2015/08/20 14:40:48]

unneeded

[Primiano Tucci (use gerrit), 2015/08/20 14:44:23]

Oh good catch. done.

+
+/**
+ * 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.
+ */
+class SK_API SkTraceMemoryDump {
+public:
+    /**
+     *  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.
+     *  Arguments:
+     *    dumpName: an absolute, slash-separated, name for the item being dumped
+     *        e.g., "skia/CacheX/EntryY".
+     *    valueName: a string indicating the name of the column.
+     *        e.g., "size", "active_size", "number_of_objects".
+     *        This string is supposed to be long lived and is NOT copied.
+     *    units: a string indicating the units for the scalar.
+     *        e.g., "bytes", "objects".
+     *        This string is supposed to be long lived and is NOT copied.
+     *    value: the actual value being dumped.
+     */
+    virtual void dumpScalarValue(const char* dumpName,

[reed1, 2015/08/20 14:40:48]

trival nit:

Skia uses the word Scalar very specifically to mean a float or double (see
SkScalar).

We can leave this here, but it might cause less confusion if this was
dumpNumericValue or dumpSingleValue or something like that.

[Primiano Tucci (use gerrit), 2015/08/20 14:44:23]

Oh I see. dumpNumericValue SGTM

+                                 const char* valueName,
+                                 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 char* dumpName,
+                                  const char* backingType,
+                                  const char* backingObjectId) = 0;
+
+    /**
+     * Specialization for memory backed by discardable memory.
+     */
+    virtual void setDiscardableMemoryBacking(
+        const char* dumpName,
+        const SkDiscardableMemory& discardableMemoryObject) = 0;
+
+protected:
+    virtual ~SkTraceMemoryDump() { }
+};
+
+#endif