[tracing] Dump child processes' memory metrics in browser

base/trace_event/process_memory_totals_dump_provider.h

Index: base/trace_event/process_memory_totals_dump_provider.h
diff --git a/base/trace_event/process_memory_totals_dump_provider.h b/base/trace_event/process_memory_totals_dump_provider.h
index 66d4f9956dd5b9144f2352f55209a249e8742017..094bef37da08feb2b13e036275e509173c89e414 100644
--- a/base/trace_event/process_memory_totals_dump_provider.h
+++ b/base/trace_event/process_memory_totals_dump_provider.h
@@ -19,7 +19,13 @@ namespace trace_event {
 // Dump provider which collects process-wide memory stats.
 class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
  public:
-  static ProcessMemoryTotalsDumpProvider* 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<ProcessMemoryTotalsDumpProvider> CreateForProcess(
+      ProcessHandle process);
+
+  ~ProcessMemoryTotalsDumpProvider() override;
 
   // MemoryDumpProvider implementation.
   bool OnMemoryDump(const MemoryDumpArgs& args,
@@ -31,9 +37,9 @@ class BASE_EXPORT ProcessMemoryTotalsDumpProvider : public MemoryDumpProvider {
 
   static uint64 rss_bytes_for_testing;
 
-  ProcessMemoryTotalsDumpProvider();
-  ~ProcessMemoryTotalsDumpProvider() override;
+  ProcessMemoryTotalsDumpProvider(ProcessHandle process);
 
+  ProcessHandle process_;
   scoped_ptr<ProcessMetrics> process_metrics_;
 
   DISALLOW_COPY_AND_ASSIGN(ProcessMemoryTotalsDumpProvider);