[WIP] Add SharedMemoryTracker to dump base::SharedMemory usage

components/discardable_memory/common/discardable_shared_memory_heap.cc

Index: components/discardable_memory/common/discardable_shared_memory_heap.cc
diff --git a/components/discardable_memory/common/discardable_shared_memory_heap.cc b/components/discardable_memory/common/discardable_shared_memory_heap.cc
index 12d8eb6cfcc1737ff64376c2fad81f2037aa86ad..2a1aad3c958b47db6f2e68e76a1fbca62f3e2391 100644
--- a/components/discardable_memory/common/discardable_shared_memory_heap.cc
+++ b/components/discardable_memory/common/discardable_shared_memory_heap.cc
@@ -11,6 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/discardable_shared_memory.h"
 #include "base/memory/ptr_util.h"
+#include "base/memory/shared_memory_tracker.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/memory_dump_manager.h"
 
@@ -440,6 +441,9 @@ void DiscardableSharedMemoryHeap::OnMemoryDump(
   // client.
   const int kImportance = 2;
   pmd->AddOwnershipEdge(segment_dump->guid(), shared_segment_guid, kImportance);
+  base::SharedMemoryTracker::AddOwnershipEdgeToSharedGlobalDump(
+      pmd, shared_segment_guid,
+      shared_memory->handle(), shared_memory->mapped_size());

[ssid, 2017/01/24 04:39:50]

Okay the right thing to do here is to keep the hierarchy of allocation and add
global dump edges only for the "sharedmemory" dumps and discardable should just
sub-allocate from the "sharedmemory/xx" objects.
So the code should look like:

base::SharedMemoryTracker::AddSuballocation(segment_dump->guid(),
shared_memory->handle(), shared_memory->mapped_size());

Also please do not add edges between 2 global dumps. The UI still does not know
how to deal with this.

 }
 
 // static