Code health: remove usage of Value::GetAsString in trace_event_memory_overhead.cc

Bug: chromium:1187007
Change-Id: Id4cefeebb6c6788e10da2e225b12ae7bb7d37cec
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3013797
Reviewed-by: ssid <ssid@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#899581}
diff --git a/base/trace_event/trace_event_memory_overhead.cc b/base/trace_event/trace_event_memory_overhead.cc
index aad17ddd..34c785a 100644
--- a/base/trace_event/trace_event_memory_overhead.cc
+++ b/base/trace_event/trace_event_memory_overhead.cc
@@ -104,10 +104,8 @@
       break;
 
     case Value::Type::STRING: {
-      const Value* string_value = nullptr;
-      value.GetAsString(&string_value);
       Add(kBaseValue, sizeof(Value));
-      AddString(string_value->GetString());
+      AddString(value.GetString());
     } break;
 
     case Value::Type::BINARY: {