Merge the Merlin heap tracing to top-of-trunk.

runtime/vm/class_table.cc

Index: runtime/vm/class_table.cc
diff --git a/runtime/vm/class_table.cc b/runtime/vm/class_table.cc
index 3b344909d61800df10b8c287bf40293e70de1492..2d14cecab2658306e78524afb043a1bfe9a76415 100644
--- a/runtime/vm/class_table.cc
+++ b/runtime/vm/class_table.cc
@@ -5,6 +5,7 @@
 #include "vm/class_table.h"
 #include "vm/flags.h"
 #include "vm/freelist.h"
+#include "vm/heap_trace.h"
 #include "vm/object.h"
 #include "vm/raw_object.h"
 #include "vm/visitor.h"
@@ -49,6 +50,9 @@ void ClassTable::Register(const Class& cls) {
     ASSERT(table_[index] == 0);
     ASSERT(index < capacity_);
     table_[index] = cls.raw();
+    if (HeapTrace::is_enabled()) {
+      Isolate::Current()->heap()->trace()->TraceRegisterClass(cls);
+    }
     // Add the vtable for this predefined class into the static vtable registry
     // if it has not been setup yet.
     cpp_vtable cls_vtable = cls.handle_vtable();
@@ -72,6 +76,9 @@ void ClassTable::Register(const Class& cls) {
     ASSERT(top_ < capacity_);
     cls.set_id(top_);
     table_[top_] = cls.raw();
+    if (HeapTrace::is_enabled()) {
+      Isolate::Current()->heap()->trace()->TraceRegisterClass(cls);
+    }
     top_++;  // Increment next index.
   }
 }