[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
+    };
+
+    explicit WebMemoryAllocatorDumpGuid(const uint64_t guid)
+        : guidInt(guid)
+        , guidString()
+        , type(IntType)
+    {
+    }
+
+    explicit WebMemoryAllocatorDumpGuid(const WebString& guid)
+        : guidInt(0)
+        , guidString(guid)
+        , type(StringType)
+    {
+    }
+
+    uint64_t guidInt;
+    WebString guidString;
+    GuidType type;
+};
+
 // A container which holds all the attributes of a particular dump for a given
 // allocator.
 class BLINK_PLATFORM_EXPORT WebMemoryAllocatorDump {
 public:
+    // TODO(ssid): This constructor should be removed once the usage is

[Primiano Tucci (use gerrit), 2015/06/08 09:39:16]

I don't think you need neither of these constructors. 
The WMAD is constructed via createMemALlocatorDump, which passes the guid to the
chromium layer.

+    // changed in chromium side (crbug.com/480500).
+    WebMemoryAllocatorDump()
+        : m_guid(WebMemoryAllocatorDumpGuid(0))
+    {
+    }
+
+    WebMemoryAllocatorDump(WebMemoryAllocatorDumpGuid guid)
+        : m_guid(guid)
+    {
+    }
+
     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) { BLINK_ASSERT_NOT_REACHED(); }
     virtual void AddScalarF(const WebString& name, const char* units, double value) { BLINK_ASSERT_NOT_REACHED(); }
     virtual void AddString(const WebString& name, const char* units, const WebString& value) { BLINK_ASSERT_NOT_REACHED(); }
+
+    // |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

[Primiano Tucci (use gerrit), 2015/06/08 09:39:16]

s/TODO_method_name/AddOwnershipEdge/

[ssid, 2015/06/08 14:29:19]

Done.

+    // 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);

[Primiano Tucci (use gerrit), 2015/06/08 09:39:16]

This should be just a virtual and the chrome layer should know how to compute
the guid.

+        return m_guid;
+    }
+
+protected:
+    WebMemoryAllocatorDumpGuid m_guid;

[Primiano Tucci (use gerrit), 2015/06/08 09:39:16]

You don't need this.
Just pass the guid you get in createMemoryAllocatorDump to the Web...Impl on the
chrome side, and store it there.

 };
 
 } // namespace blink
 
 #endif // WebMemoryAllocatorDump_h