Add support to trace warnings in TraceBuffer.

runtime/vm/exceptions.cc

Index: runtime/vm/exceptions.cc
===================================================================
--- runtime/vm/exceptions.cc	(revision 37220)
+++ runtime/vm/exceptions.cc	(working copy)
@@ -750,16 +750,18 @@
   ASSERT(caller_frame != NULL);
   ASSERT(FLAG_warn_on_javascript_compatibility);
   if (FLAG_silent_warnings) return;
-  const Code& caller_code = Code::Handle(caller_frame->LookupDartCode());
+  Isolate* isolate = Isolate::Current();
+  const Code& caller_code = Code::Handle(isolate,
+                                         caller_frame->LookupDartCode());
   ASSERT(!caller_code.IsNull());
   const uword caller_pc = caller_frame->pc();
   const intptr_t token_pos = caller_code.GetTokenIndexOfPC(caller_pc);
-  const Function& caller = Function::Handle(caller_code.function());
-  const Script& script = Script::Handle(caller.script());
+  const Function& caller = Function::Handle(isolate, caller_code.function());
+  const Script& script = Script::Handle(isolate, caller.script());
   va_list args;
   va_start(args, format);
-  const Error& error = Error::Handle(
-      LanguageError::NewFormattedV(Error::Handle(),  // No previous error.
+  const Error& error = Error::Handle(isolate,
+      LanguageError::NewFormattedV(Error::Handle(isolate),  // No prev error.
                                    script, token_pos, LanguageError::kWarning,
                                    Heap::kNew, format, args));
   va_end(args);
@@ -767,9 +769,12 @@
     ThrowJavascriptCompatibilityError(error.ToErrorCString());
   } else {
     OS::Print("javascript compatibility warning: %s", error.ToErrorCString());
+    va_start(args, format);
+    TraceBuffer::TraceWarningV(isolate, script, token_pos, format, args);
+    va_end(args);
   }
   const Stacktrace& stacktrace =
-     Stacktrace::Handle(Exceptions::CurrentStacktrace());
+     Stacktrace::Handle(isolate, Exceptions::CurrentStacktrace());
   intptr_t idx = 0;
   OS::Print("%s",
             stacktrace.ToCStringInternal(&idx,