trace_event: Add FrameMetrics memory overhead type.

Bug: 790759
Change-Id: I4655e5763198a6eab8b407f36383f756d8484ba6
Reviewed-on: https://chromium-review.googlesource.com/1072878Reviewed-by: Primiano Tucci <primiano@chromium.org>
Commit-Queue: Brian Anderson <brianderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#563087}

base/trace_event/trace_event_memory_overhead.cc

@@ -47,6 +47,8 @@ const char* ObjectTypeToString(TraceEventMemoryOverhead::ObjectType type) {
       return "base::Value";
     case TraceEventMemoryOverhead::kTraceEventMemoryOverhead:
       return "TraceEventMemoryOverhead";
+    case TraceEventMemoryOverhead::kFrameMetrics:
+      return "FrameMetrics";
     case TraceEventMemoryOverhead::kLast:
       NOTREACHED();
   }

base/trace_event/trace_event_memory_overhead.h

@@ -39,6 +39,7 @@ class BASE_EXPORT TraceEventMemoryOverhead {
     kStdString,
     kBaseValue,
     kTraceEventMemoryOverhead,
+    kFrameMetrics,
     kLast
   };