[Sync] Implement EstimateMemoryUsage for SharedModelTypeProcessor and ModelTypeWorker

components/sync/base/proto_value_ptr.h

Index: components/sync/base/proto_value_ptr.h
diff --git a/components/sync/base/proto_value_ptr.h b/components/sync/base/proto_value_ptr.h
index 89189b9412d383c88fe31f68d65338c7e4b32710..cd4a1ca17665691d94a11ad677d2dd64e58e47f8 100644
--- a/components/sync/base/proto_value_ptr.h
+++ b/components/sync/base/proto_value_ptr.h
@@ -7,6 +7,7 @@
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/trace_event/memory_usage_estimator.h"
 
 namespace syncer {
 
@@ -127,6 +128,7 @@ class ProtoValuePtr {
 
 template <typename T, typename Traits>
 size_t EstimateMemoryUsage(const ProtoValuePtr<T, Traits>& ptr) {
+  using base::trace_event::EstimateMemoryUsage;

[Patrick Noland, 2017/03/29 19:42:54]

Can you add a comment explaining what this is for? IIRC it's to resolve the
ambiguity between two definitions of EstimateMemoryUsage?

[pavely, 2017/03/30 01:07:24]

Done.

   return &ptr.value() != &Traits::DefaultValue()
              ? EstimateMemoryUsage(ptr.value())
              : 0;