[turbofan] Assign better types to various String builtins.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index b2593b9af7bb2308a336f8d0c71e89aa30509799..08e42b45e47331a1f065bb64006397c165432c22 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -6555,37 +6555,40 @@ class Script: public Struct {
 //
 // Installation of ids for the selected builtin functions is handled
 // by the bootstrapper.
-#define FUNCTIONS_WITH_ID_LIST(V)                   \
-  V(Array.prototype, indexOf, ArrayIndexOf)         \
-  V(Array.prototype, lastIndexOf, ArrayLastIndexOf) \
-  V(Array.prototype, push, ArrayPush)               \
-  V(Array.prototype, pop, ArrayPop)                 \
-  V(Array.prototype, shift, ArrayShift)             \
-  V(Function.prototype, apply, FunctionApply)       \
-  V(Function.prototype, call, FunctionCall)         \
-  V(String.prototype, charCodeAt, StringCharCodeAt) \
-  V(String.prototype, charAt, StringCharAt)         \
-  V(String, fromCharCode, StringFromCharCode)       \
-  V(Math, random, MathRandom)                       \
-  V(Math, floor, MathFloor)                         \
-  V(Math, round, MathRound)                         \
-  V(Math, ceil, MathCeil)                           \
-  V(Math, abs, MathAbs)                             \
-  V(Math, log, MathLog)                             \
-  V(Math, exp, MathExp)                             \
-  V(Math, sqrt, MathSqrt)                           \
-  V(Math, pow, MathPow)                             \
-  V(Math, max, MathMax)                             \
-  V(Math, min, MathMin)                             \
-  V(Math, cos, MathCos)                             \
-  V(Math, sin, MathSin)                             \
-  V(Math, tan, MathTan)                             \
-  V(Math, acos, MathAcos)                           \
-  V(Math, asin, MathAsin)                           \
-  V(Math, atan, MathAtan)                           \
-  V(Math, atan2, MathAtan2)                         \
-  V(Math, imul, MathImul)                           \
-  V(Math, clz32, MathClz32)                         \
+#define FUNCTIONS_WITH_ID_LIST(V)                     \
+  V(Array.prototype, indexOf, ArrayIndexOf)           \
+  V(Array.prototype, lastIndexOf, ArrayLastIndexOf)   \
+  V(Array.prototype, push, ArrayPush)                 \
+  V(Array.prototype, pop, ArrayPop)                   \
+  V(Array.prototype, shift, ArrayShift)               \
+  V(Function.prototype, apply, FunctionApply)         \
+  V(Function.prototype, call, FunctionCall)           \
+  V(String.prototype, charCodeAt, StringCharCodeAt)   \
+  V(String.prototype, charAt, StringCharAt)           \
+  V(String.prototype, concat, StringConcat)           \
+  V(String.prototype, toLowerCase, StringToLowerCase) \
+  V(String.prototype, toUpperCase, StringToUpperCase) \
+  V(String, fromCharCode, StringFromCharCode)         \
+  V(Math, random, MathRandom)                         \
+  V(Math, floor, MathFloor)                           \
+  V(Math, round, MathRound)                           \
+  V(Math, ceil, MathCeil)                             \
+  V(Math, abs, MathAbs)                               \
+  V(Math, log, MathLog)                               \
+  V(Math, exp, MathExp)                               \
+  V(Math, sqrt, MathSqrt)                             \
+  V(Math, pow, MathPow)                               \
+  V(Math, max, MathMax)                               \
+  V(Math, min, MathMin)                               \
+  V(Math, cos, MathCos)                               \
+  V(Math, sin, MathSin)                               \
+  V(Math, tan, MathTan)                               \
+  V(Math, acos, MathAcos)                             \
+  V(Math, asin, MathAsin)                             \
+  V(Math, atan, MathAtan)                             \
+  V(Math, atan2, MathAtan2)                           \
+  V(Math, imul, MathImul)                             \
+  V(Math, clz32, MathClz32)                           \
   V(Math, fround, MathFround)
 
 #define ATOMIC_FUNCTIONS_WITH_ID_LIST(V) \