Merge r6773 to 2.5 branch.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
===================================================================
--- src/arm/macro-assembler-arm.cc	(revision 6773)
+++ src/arm/macro-assembler-arm.cc	(working copy)
@@ -1747,6 +1747,18 @@
 }
 
 
+void MacroAssembler::AbortIfNotString(Register object) {
+  STATIC_ASSERT(kSmiTag == 0);
+  tst(object, Operand(kSmiTagMask));
+  Assert(ne, "Operand is not a string");
+  push(object);
+  ldr(object, FieldMemOperand(object, HeapObject::kMapOffset));
+  CompareInstanceType(object, object, FIRST_NONSTRING_TYPE);
+  pop(object);
+  Assert(lo, "Operand is not a string");
+}
+
+
 void MacroAssembler::JumpIfNonSmisNotBothSequentialAsciiStrings(
     Register first,
     Register second,