Use 'new' in all the snapshot reallocation functions instead of realloc.

runtime/vm/code_observers.cc

Index: runtime/vm/code_observers.cc
===================================================================
--- runtime/vm/code_observers.cc	(revision 23633)
+++ runtime/vm/code_observers.cc	(working copy)
@@ -4,6 +4,7 @@
 
 #include "vm/code_observers.h"
 
+#include "platform/utils.h"
 #include "vm/os.h"
 
 namespace dart {
@@ -13,12 +14,12 @@
 
 
 void CodeObservers::Register(CodeObserver* observer) {
-  observers_length_++;
-  observers_ = reinterpret_cast<CodeObserver**>(
-      realloc(observers_, sizeof(observer) * observers_length_));
+  intptr_t new_length = observers_length_ + 1;
+  observers_ = Utils::Realloc(observers_, observers_length_, new_length);
   if (observers_ == NULL) {
     FATAL("failed to grow code observers array");
   }
+  observers_length_ = new_length;
   observers_[observers_length_ - 1] = observer;
 }