Correct a misuse of sizeof (introduced in r22709).

src/runtime.cc

Index: src/runtime.cc
diff --git a/src/runtime.cc b/src/runtime.cc
index 7afa3a6aa6e6122bc1932a2a320d3077684d18d9..63d6ea2da831449eb4c31f0786da60e4deee2d53 100644
--- a/src/runtime.cc
+++ b/src/runtime.cc
@@ -15591,7 +15591,8 @@ const Runtime::Function* Runtime::FunctionForName(Handle<String> name) {
 
 
 const Runtime::Function* Runtime::FunctionForEntry(Address entry) {
-  for (size_t i = 0; i < sizeof(kIntrinsicFunctions); ++i) {
+  size_t length = sizeof(kIntrinsicFunctions) / sizeof(*kIntrinsicFunctions);
+  for (size_t i = 0; i < length; ++i) {
     if (entry == kIntrinsicFunctions[i].entry) {
       return &(kIntrinsicFunctions[i]);
     }