Extract hardcoded error strings into a single place and replace them with enum.

src/mips/codegen-mips.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 271 matching lines @@
 
   __ Branch(&entry);
 
   // Hole found, store the-hole NaN.
   __ bind(&convert_hole);
   if (FLAG_debug_code) {
     // Restore a "smi-untagged" heap object.
     __ SmiTag(t5);
     __ Or(t5, t5, Operand(1));
     __ LoadRoot(at, Heap::kTheHoleValueRootIndex);
-    __ Assert(eq, "object found in smi-only array", at, Operand(t5));
+    __ Assert(eq, kObjectFoundInSmiOnlyArray, at, Operand(t5));
   }
   __ sw(t0, MemOperand(t3));  // mantissa
   __ sw(t1, MemOperand(t3, kIntSize));  // exponent
   __ Addu(t3, t3, kDoubleSize);
 
   __ bind(&entry);
   __ Branch(&loop, lt, t3, Operand(t2));
 
   __ pop(ra);
   __ bind(&done);
@@ skipping 179 matching lines @@
           string,
           SeqTwoByteString::kHeaderSize - kHeapObjectTag);
   __ jmp(&check_encoding);
 
   // Handle external strings.
   __ bind(&external_string);
   if (FLAG_debug_code) {
     // Assert that we do not have a cons or slice (indirect strings) here.
     // Sequential strings have already been ruled out.
     __ And(at, result, Operand(kIsIndirectStringMask));
-    __ Assert(eq, "external string expected, but not found",
+    __ Assert(eq, kExternalStringExpectedButNotFound,
         at, Operand(zero_reg));
   }
   // Rule out short external strings.
   STATIC_CHECK(kShortExternalStringTag != 0);
   __ And(at, result, Operand(kShortExternalStringMask));
   __ Branch(call_runtime, ne, at, Operand(zero_reg));
   __ lw(string, FieldMemOperand(string, ExternalString::kResourceDataOffset));
 
   Label ascii, done;
   __ bind(&check_encoding);
@@ skipping 156 matching lines @@
     patcher.masm()->dd(reinterpret_cast<uint32_t>(stub->instruction_start()));
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_MIPS