Heap::AllocateStringFromOneByte() and major part of its callers handlified.

src/isolate.cc

Index: src/isolate.cc
diff --git a/src/isolate.cc b/src/isolate.cc
index 5feb48eeff19f00c404e55603d357a9722a4b8fa..7370aa7958825c00a69a2dded4784fa9e0914853 100644
--- a/src/isolate.cc
+++ b/src/isolate.cc
@@ -324,6 +324,7 @@ Handle<String> Isolate::StackTraceString() {
     StringStream accumulator(&allocator);
     incomplete_message_ = &accumulator;
     PrintStack(&accumulator);
+    // TODO(ishell): Can this fail??
     Handle<String> stack_trace = accumulator.ToString(this);
     incomplete_message_ = NULL;
     stack_trace_nesting_level_ = 0;