[Sync] Rework SharedValue<T> into Immutable<T>

chrome/browser/sync/js/js_event_details.cc

Index: chrome/browser/sync/js/js_event_details.cc
diff --git a/chrome/browser/sync/js/js_event_details.cc b/chrome/browser/sync/js/js_event_details.cc
index ae23d1790f60ca3342f08975a09382e8f92fccb5..9182d24c923236c4bd57a41fbba0baf8a5e794a1 100644
--- a/chrome/browser/sync/js/js_event_details.cc
+++ b/chrome/browser/sync/js/js_event_details.cc
@@ -8,16 +8,14 @@
 
 namespace browser_sync {
 
-JsEventDetails::JsEventDetails()
-    : details_(new SharedDictionaryValue()) {}
+JsEventDetails::JsEventDetails() {}
 
-JsEventDetails::JsEventDetails(DictionaryValue* details)
-    : details_(new SharedDictionaryValue(details)) {}
+JsEventDetails::JsEventDetails(DictionaryValue* details) : details_(details) {}
 
 JsEventDetails::~JsEventDetails() {}
 
 const DictionaryValue& JsEventDetails::Get() const {
-  return details_->Get();
+  return details_.Get();
 }
 
 std::string JsEventDetails::ToString() const {