[tracing] Dump child processes' memory metrics in browser

base/trace_event/process_memory_maps_dump_provider.h

Index: base/trace_event/process_memory_maps_dump_provider.h
diff --git a/base/trace_event/process_memory_maps_dump_provider.h b/base/trace_event/process_memory_maps_dump_provider.h
index f302a48dd7da182f587545e929f75ed3f91baf97..d81ce6a0ecf5fc967e81b2dace4cc828a09872f9 100644
--- a/base/trace_event/process_memory_maps_dump_provider.h
+++ b/base/trace_event/process_memory_maps_dump_provider.h
@@ -15,7 +15,13 @@ namespace trace_event {
 // Dump provider which collects process-wide memory stats.
 class BASE_EXPORT ProcessMemoryMapsDumpProvider : public MemoryDumpProvider {
  public:
-  static ProcessMemoryMapsDumpProvider* GetInstance();
+  // Creates a dump provider for a child process with |process_id|.
+  // Note: Current Process should be able to access process metrics of the
+  // process, else this method returns empty ptr.
+  static scoped_ptr<ProcessMemoryMapsDumpProvider> CreateForProcess(

[Primiano Tucci (use gerrit), 2015/11/03 15:14:08]

this cannot be a singleton and a non-singleton at the same time.
de-singletonify?

+      ProcessHandle process);
+
+  ~ProcessMemoryMapsDumpProvider() override;
 
   // MemoryDumpProvider implementation.
   bool OnMemoryDump(const MemoryDumpArgs& args,
@@ -29,8 +35,9 @@ class BASE_EXPORT ProcessMemoryMapsDumpProvider : public MemoryDumpProvider {
   static FILE* proc_smaps_for_testing;
 #endif
 
-  ProcessMemoryMapsDumpProvider();
-  ~ProcessMemoryMapsDumpProvider() override;
+  ProcessMemoryMapsDumpProvider(ProcessHandle process);
+
+  ProcessHandle process_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryMapsDumpProvider);
 };