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

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index ec51dc59733ab460df4225b10d46bcfb429213a4..7b5a5d0f86f4a7848b9b64bd1ab50fd784f4cf78 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -578,6 +578,12 @@ public:
     // Returns a newly allocated WebProcessMemoryDump instance.
     virtual blink::WebProcessMemoryDump* createProcessMemoryDump() { return nullptr; }
 
+    typedef uint64_t WebMemoryAllocatorDumpGuid;
+
+    // Returns guid corresponding to the given string (the hash value) for
+    // creating a WebMemoryAllocatorDump.
+    virtual WebMemoryAllocatorDumpGuid createWebMemoryAllocatorDumpGuid(const WebString& guidStr) { return 0; }
+
     // GPU ----------------------------------------------------------------
     //
     // May return null if GPU is not supported.