[tracing] Add support to pre-load and merge ProcessMemoryDump(s).

base/trace_event/process_memory_dump.h

Index: base/trace_event/process_memory_dump.h
diff --git a/base/trace_event/process_memory_dump.h b/base/trace_event/process_memory_dump.h
index 889356d65aa57d8599a715ab4cdb5ad062d2aa82..9ffd89b61dfdc5ee7e03e9f1c484dfabaa2a9b36 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -41,6 +41,15 @@ class BASE_EXPORT ProcessMemoryDump {
   // Called at trace generation time to populate the TracedValue.
   void AsValueInto(TracedValue* value) const;
 
+  // Merges all the MemoryAllocatorDump(s) contained in |other| inside this

[petrcermak, 2015/05/21 08:17:38]

I don't think you need "the" in front of "MemoryAllocatorDump(s)".

[Primiano Tucci (use gerrit), 2015/05/21 08:33:46]

Done.

+  // ProcessMemoryDump, moving their ownership to this instance. |other| will

[petrcermak, 2015/05/21 08:17:38]

"transfer ownership" seems to be used much more often than "move ownership".

[Primiano Tucci (use gerrit), 2015/05/21 08:33:46]

Done.

+  // be an empty ProcessMemoryDump after this method returns.
+  // This is to allow dump providers to create and populate out-of-band

[petrcermak, 2015/05/21 08:17:38]

nit: I know what you mean, but "out-of-band" is not very clear to me. Maybe
"out-of-sync"?

[Primiano Tucci (use gerrit), 2015/05/21 08:33:46]

reworded

+  // instances of ProcessMemoryDump and later move them into the

[petrcermak, 2015/05/21 08:17:38]

nit: The *contents* of the PMD instances are moved (not the instances
themselves).

[Primiano Tucci (use gerrit), 2015/05/21 08:33:46]

reworded

+  // ProcessMemoryDump passed as argument of the
+  // MemoryDumpProvider.OnMemoryDump(ProcessMemoryDump*) callback.
+  void TakeAllDumpsFrom(ProcessMemoryDump* other);
+
   ProcessMemoryTotals* process_totals() { return &process_totals_; }
   bool has_process_totals() const { return has_process_totals_; }
   void set_has_process_totals() { has_process_totals_ = true; }