[memory-infra] Add method to override importance of ownership edges

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 45a973964231fa7d794b2be72d3175871970720b..521c381506c8e13c64fcc01763476a44b7ef0c03 100644
--- a/base/trace_event/process_memory_dump.h
+++ b/base/trace_event/process_memory_dump.h
@@ -7,6 +7,7 @@
 
 #include <stddef.h>
 
+#include <map>
 #include <unordered_map>
 #include <vector>
 
@@ -39,10 +40,10 @@ class TracedValue;
 class BASE_EXPORT ProcessMemoryDump {
  public:
   struct MemoryAllocatorDumpEdge {
-    MemoryAllocatorDumpGuid source;
     MemoryAllocatorDumpGuid target;
     int importance;
     const char* type;
+    bool overridable;
   };
 
   // Maps allocator dumps absolute names (allocator_name/heap/subheap) to
@@ -53,6 +54,11 @@ class BASE_EXPORT ProcessMemoryDump {
   using HeapDumpsMap =
       std::unordered_map<std::string, std::unique_ptr<TracedValue>>;
 
+  // Stores allocator dump edges as a map from source allocator dump guids to
+  // the target.

[Primiano Tucci (use gerrit), 2017/06/05 15:23:39]

"to the target" part  in the comment  is false :) (but the code makes sense).
I think you just want to say "indexed by source allocator GUID"

[ssid, 2017/06/05 17:03:29]

Yeah, I was looking for this phrase!

+  using AllocatorDumpEdgesMap =
+      std::map<MemoryAllocatorDumpGuid, MemoryAllocatorDumpEdge>;
+
 #if defined(COUNT_RESIDENT_BYTES_SUPPORTED)
   // Returns the number of bytes in a kernel memory page. Some platforms may
   // have a different value for kernel page sizes from user page sizes. It is
@@ -135,7 +141,7 @@ class BASE_EXPORT ProcessMemoryDump {
   void AddOwnershipEdge(const MemoryAllocatorDumpGuid& source,
                         const MemoryAllocatorDumpGuid& target);
 
-  const std::vector<MemoryAllocatorDumpEdge>& allocator_dumps_edges() const {
+  const AllocatorDumpEdgesMap& allocator_dumps_edges_for_testing() const {
     return allocator_dumps_edges_;
   }
 
@@ -181,12 +187,20 @@ class BASE_EXPORT ProcessMemoryDump {
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ProcessMemoryDumpTest, BackgroundModeTest);
+  FRIEND_TEST_ALL_PREFIXES(ProcessMemoryDumpTest, OverrideOwnershipEdge);
 
   MemoryAllocatorDump* AddAllocatorDumpInternal(
       std::unique_ptr<MemoryAllocatorDump> mad);
 
   MemoryAllocatorDump* GetBlackHoleMad();
 
+  // Adds edges that can be overriden by a later or earlier call to
+  // AddOwnershipEdge() with the same source and target with a different
+  // |importance| value.
+  void AddOverridableOwnershipEdge(const MemoryAllocatorDumpGuid& source,
+                                   const MemoryAllocatorDumpGuid& target,
+                                   int importance);
+
   ProcessMemoryTotals process_totals_;
   bool has_process_totals_;
 
@@ -200,7 +214,7 @@ class BASE_EXPORT ProcessMemoryDump {
   scoped_refptr<MemoryDumpSessionState> session_state_;
 
   // Keeps track of relationships between MemoryAllocatorDump(s).
-  std::vector<MemoryAllocatorDumpEdge> allocator_dumps_edges_;
+  AllocatorDumpEdgesMap allocator_dumps_edges_;
 
   // Level of detail of the current dump.
   const MemoryDumpArgs dump_args_;