Add a field platform_private_footprint_ to ProcessMemoryTotals.

base/trace_event/process_memory_totals.cc

Index: base/trace_event/process_memory_totals.cc
diff --git a/base/trace_event/process_memory_totals.cc b/base/trace_event/process_memory_totals.cc
index de27ab3d9d441a939f87ffa898e46d1bf8520a90..4a9aaba67199728fbbd16beee365cff8091a2125 100644
--- a/base/trace_event/process_memory_totals.cc
+++ b/base/trace_event/process_memory_totals.cc
@@ -14,8 +14,8 @@ namespace trace_event {
 ProcessMemoryTotals::ProcessMemoryTotals()
     : resident_set_bytes_(0),
       peak_resident_set_bytes_(0),
-      is_peak_rss_resetable_(false) {
-}
+      is_peak_rss_resetable_(false),
+      private_footprint_precursor_(0) {}
 
 ProcessMemoryTotals::~ProcessMemoryTotals() {}
 
@@ -35,6 +35,7 @@ void ProcessMemoryTotals::AsValueInto(TracedValue* value) const {
 
 void ProcessMemoryTotals::Clear() {
   resident_set_bytes_ = 0;
+  private_footprint_precursor_ = 0;
 }
 
 void ProcessMemoryTotals::SetExtraFieldInBytes(const char* name,