[memory-infra] Implement PollFastMemoryTotal in ProcessMetricsMemoryDumpProvider.

components/tracing/common/process_metrics_memory_dump_provider.h

Index: components/tracing/common/process_metrics_memory_dump_provider.h
diff --git a/components/tracing/common/process_metrics_memory_dump_provider.h b/components/tracing/common/process_metrics_memory_dump_provider.h
index b47bdec142b7145feaf31af18dd4a7ecaad61010..3066f9d02164b8f0eeb994b3b96ab283c3950c0f 100644
--- a/components/tracing/common/process_metrics_memory_dump_provider.h
+++ b/components/tracing/common/process_metrics_memory_dump_provider.h
@@ -33,11 +33,15 @@ class TRACING_EXPORT ProcessMetricsMemoryDumpProvider
   // MemoryDumpProvider implementation.
   bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
                     base::trace_event::ProcessMemoryDump* pmd) override;
+  void PollFastMemoryTotal(uint64_t* memory_total) override;
+  void SetFastMemoryPollingEnabled(bool enabled) override;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(ProcessMetricsMemoryDumpProviderTest,
                            ParseProcSmaps);
   FRIEND_TEST_ALL_PREFIXES(ProcessMetricsMemoryDumpProviderTest, DumpRSS);
+  FRIEND_TEST_ALL_PREFIXES(ProcessMetricsMemoryDumpProviderTest,
+                           TestPollFastMemoryTotal);
 
   ProcessMetricsMemoryDumpProvider(base::ProcessId process);
 
@@ -50,6 +54,12 @@ class TRACING_EXPORT ProcessMetricsMemoryDumpProvider
 
 #if defined(OS_LINUX) || defined(OS_ANDROID)
   static FILE* proc_smaps_for_testing;
+
+  void set_fast_polling_statm_fd_for_testing(int fd) {

[Primiano Tucci (use gerrit), 2016/12/15 15:00:02]

maybe use the same pattern as above:

static int proc_statm_for_testing;

and when you get to open the file, check if this field is non-zero.
THe current design is a bit odd because you first have to open the real
/proc/xxx/statm file and *then* override with this function.

[ssid, 2016/12/16 03:16:41]

Done.

+    fast_polling_statm_fd_ = fd;
+  }
+
+  int fast_polling_statm_fd_;
 #endif
 
   base::ProcessId process_;