Store a base::Location in syncer::syncable::WriteTransactionInfo

This class used to hold the location as a string, since base::Location
wasn't assignable. It is now.

Bug: 764195
Change-Id: I81a04d2ecc981c39f0e0bcb54cb76e6ee87248f8
Reviewed-on: https://chromium-review.googlesource.com/664220Reviewed-by: Brett Wilson <brettw@chromium.org>
Reviewed-by: Stanislav Chiknavaryan <stanisc@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501455}

components/sync/syncable/write_transaction_info.cc

@@ -17,10 +17,7 @@ WriteTransactionInfo::WriteTransactionInfo(
     base::Location location,
     WriterTag writer,
     ImmutableEntryKernelMutationMap mutations)
-    : id(id),
-      location_string(location.ToString()),
-      writer(writer),
-      mutations(mutations) {}
+    : id(id), location_(location), writer(writer), mutations(mutations) {}
 
 WriteTransactionInfo::WriteTransactionInfo() : id(-1), writer(INVALID) {}
 
@@ -33,7 +30,7 @@ std::unique_ptr<base::DictionaryValue> WriteTransactionInfo::ToValue(
     size_t max_mutations_size) const {
   auto dict = std::make_unique<base::DictionaryValue>();
   dict->SetString("id", base::Int64ToString(id));
-  dict->SetString("location", location_string);
+  dict->SetString("location", location_.ToString());
   dict->SetString("writer", WriterTagToString(writer));
   std::unique_ptr<base::Value> mutations_value;
   const size_t mutations_size = mutations.Get().size();

components/sync/syncable/write_transaction_info.h

@@ -32,9 +32,7 @@ struct WriteTransactionInfo {
       size_t max_mutations_size) const;
 
   int64_t id;
-  // If base::Location becomes assignable, we can use that
-  // instead.
-  std::string location_string;
+  base::Location location_;
   WriterTag writer;
   ImmutableEntryKernelMutationMap mutations;
 };