Remove strong mode support from binary operations.

test/mjsunit/messages.js

Index: test/mjsunit/messages.js
diff --git a/test/mjsunit/messages.js b/test/mjsunit/messages.js
index 772670a06c3de3eb1e2a496957b53282e9496df1..013d2739c5d4efe6cf0dc83af3e56e0aca703bf4 100644
--- a/test/mjsunit/messages.js
+++ b/test/mjsunit/messages.js
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 // Flags: --stack-size=100 --harmony --harmony-reflect --harmony-regexps
-// Flags: --harmony-simd --strong-mode
+// Flags: --harmony-simd
 
 function test(f, expected, type) {
   try {
@@ -305,12 +305,6 @@ test(function() {
   (1).a = 1;
 }, "Cannot create property 'a' on number '1'", TypeError);
 
-// kStrongImplicitCast
-test(function() {
-  "use strong";
-  "a" + 1;
-}, "In strong mode, implicit conversions are deprecated", TypeError);
-
 // kSymbolToString
 test(function() {
   "" + Symbol();