[tracing] Add method to create "weak" global dumps

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 5a6640288170783cd0c77c3580bf5c427dbe3312..c99fb65a8e8e90965a37c73bad5d32f5a1a5e360 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -98,6 +98,14 @@ class BASE_EXPORT ProcessMemoryDump {
   MemoryAllocatorDump* CreateSharedGlobalAllocatorDump(
       const MemoryAllocatorDumpGuid& guid);
 
+  // Creates a shared MemoryAllocatorDump as CreateSharedGlobalAllocatorDump,
+  // but with "WEAK" flag. A weak dump will be removed unless a non-weak dump

[petrcermak, 2016/01/18 11:23:46]

nit: I'd drop the quotes and add an indefinite article in front of 'WEAK'.

[ssid, 2016/01/18 16:28:36]

Done.

+  // is created using CreateSharedGlobalAllocatorDump by at least one process
+  // (order of creation does not matter). All the owners and children of the

[petrcermak, 2016/01/18 11:23:46]

nit: s/the owners/owners/

[ssid, 2016/01/18 16:28:36]

Done.

+  // removed dump will also be removed transitively.
+  MemoryAllocatorDump* CreateWeakSharedGlobalAllocatorDump(
+      const MemoryAllocatorDumpGuid& guid);
+
   // Looks up a shared MemoryAllocatorDump given its guid.
   MemoryAllocatorDump* GetSharedGlobalAllocatorDump(
       const MemoryAllocatorDumpGuid& guid) const;