Fix Vtune support to handle deprecation of V8_USE_UNSAFE_HANDLES

In revision 15142, the V8_USE_UNSAFE_HANDLES define is removed. 

So in the vtune support code ( in vtune-jit.cc file)v8::Handle<T* value> consturctor cannot be invoked directly.
We use "->ToString()" to create the Handle<String> object  to fix the compilation error.

R=danno@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=15299

[danno, 2013-06-24 14:01:47]

Please update the subject of the CL to be more appropriate to the change and
then I will land this for you, e.g.:

Fix Vtune support to handle deprecation of V8_USE_UNSAFE_HANDLES

[chunyang.dai, 2013-06-24 14:06:18]

Hello, Daniel. 
I updated it.  please review it. 

Thanks.

[danno, 2013-06-24 14:21:07]

lgtm

[danno, 2013-06-24 14:21:20]

Committed patchset #1 manually as r15299 (presubmit successful).