Rolling back r10049 due to webkit failures.

src/heap-inl.h

Index: src/heap-inl.h
diff --git a/src/heap-inl.h b/src/heap-inl.h
index 8977cdb460213806429a6937fa2ac883be5c77f6..396f6789284e1cfa6d56d03b0e3581da6e55a760 100644
--- a/src/heap-inl.h
+++ b/src/heap-inl.h
@@ -255,11 +255,16 @@ void Heap::FinalizeExternalString(String* string) {
           ExternalString::kResourceOffset -
           kHeapObjectTag);
 
+  // Clear pointer cache.
+  ExternalString::cast(string)->clear_data_cache();
+
   // Dispose of the C++ object if it has not already been disposed.
   if (*resource_addr != NULL) {
     (*resource_addr)->Dispose();
-    *resource_addr = NULL;
   }
+
+  // Clear the resource pointer in the string.
+  *resource_addr = NULL;
 }