Fix signed / unsigned warnings for ?: operators reported by Xcode 4.x clang compiler.

src/api.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 507 matching lines @@
 }
 
 
 Extension::Extension(const char* name,
                      const char* source,
                      int dep_count,
                      const char** deps,
                      int source_length)
     : name_(name),
       source_length_(source_length >= 0 ?
-                  source_length : (source ? strlen(source) : 0)),
+                     source_length :
+                     (source ? static_cast<int>(strlen(source)) : 0)),
       source_(source, source_length_),
       dep_count_(dep_count),
       deps_(deps),
       auto_enable_(false) { }
 
 
 v8::Handle<Primitive> Undefined() {
   i::Isolate* isolate = i::Isolate::Current();
   if (!EnsureInitializedForIsolate(isolate, "v8::Undefined()")) {
     return v8::Handle<v8::Primitive>();
@@ skipping 5655 matching lines @@
 
 
 char* HandleScopeImplementer::Iterate(ObjectVisitor* v, char* storage) {
   HandleScopeImplementer* scope_implementer =
       reinterpret_cast<HandleScopeImplementer*>(storage);
   scope_implementer->IterateThis(v);
   return storage + ArchiveSpacePerThread();
 }
 
 } }  // namespace v8::internal