[tracing] Expose AddOwnershipEdge and CreateAllocatorDump with guid to blink. (blink-side).

public/platform/WebMemoryAllocatorDump.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebMemoryAllocatorDump_h
 #define WebMemoryAllocatorDump_h
 
 #include "WebCommon.h"
 #include "WebString.h"
 
 namespace blink {
 
+// Struct which has the guid of the WebMemoryAllocatorDump. The guid can either
+// be uint64_t or WebString.
+struct BLINK_PLATFORM_EXPORT WebMemoryAllocatorDumpGuid {
+public:
+    enum GuidType {
+        IntType,
+        StringType
+    };
+
+    uint64_t guidInt;

[Primiano Tucci (use gerrit), 2015/06/02 12:38:52]

is this the right order in blink? Shouldn't these go last? Please check

[ssid, 2015/06/02 16:08:02]

There is one place where it is in this order, thought that was right.

+    WebString guidString;
+    GuidType type;
+
+    explicit WebMemoryAllocatorDumpGuid(const uint64_t guid)
+        : guidInt(guid)
+        , guidString()
+        , type(IntType)
+    {
+    }
+
+    explicit WebMemoryAllocatorDumpGuid(const WebString& guid)
+        : guidInt(0)
+        , guidString(guid)
+        , type(StringType)
+    {
+    }
+};
+
 // A container which holds all the attributes of a particular dump for a given
 // allocator.
 class BLINK_PLATFORM_EXPORT WebMemoryAllocatorDump {
 public:
+    WebMemoryAllocatorDump()
+        : m_guid(WebMemoryAllocatorDumpGuid(0))

[Primiano Tucci (use gerrit), 2015/06/02 12:38:52]

I am not sure I understand this. Why the guid is just not passed as an arg of
the ctor?
It seems odd that here you initialize it with an invalid value, and on the other
side you set the protected.
Or if you prefer you can just not store anything here and make the getter
virtual, and do the conversion in content/

[ssid, 2015/06/02 16:08:02]

Done.

+    {
+    }
+
     virtual ~WebMemoryAllocatorDump();
 
     // Adds a scalar attribute to the dump.
     // Arguments:
     //   name: name of the attribute. Typical names, emitted by most allocators
     //       dump providers are: "outer_size", "inner_size", "objects_count".
     //   units: the units for the attribute. Gives a hint to the trace-viewer UI
     //       about the semantics of the attribute.
     //       Currently supported values are "bytes" and "objects".
     //   value: the value of the attribute.
     virtual void AddScalar(const WebString& name, const char* units, uint64_t value) { }
     virtual void AddString(const WebString& name, const char* units, const WebString& value) { }
+
+    // |guid| is an optional global dump identifier, unique across all processes
+    // within the scope of a global dump. It is only required when using the
+    // graph APIs (see TODO_method_name) to express retention / suballocation or
+    // cross process sharing. See crbug.com/492102 for design docs.
+    // Subsequent MemoryAllocatorDump(s) with the same |absolute_name| are
+    // expected to have the same guid. Always returns WebMemoryAllocatorDumpGuid
+    // with IntType.
+    const WebMemoryAllocatorDumpGuid& guid() const
+    {
+        BLINK_ASSERT(m_guid.guidInt);
+        return m_guid;
+    }
+
+protected:
+    WebMemoryAllocatorDumpGuid m_guid;
 };
 
 } // namespace blink
 
 #endif // WebMemoryAllocatorDump_h