Remove --stop-at flag from several backends.

src/crankshaft/mips64/lithium-codegen-mips64.cc

Index: src/crankshaft/mips64/lithium-codegen-mips64.cc
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.cc b/src/crankshaft/mips64/lithium-codegen-mips64.cc
index 89e5eb874c9ad4bdafefc30371d997b380c65f59..b0fd0952ce7b125281d41b675b154589e1ccd1aa 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.cc
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.cc
@@ -102,13 +102,6 @@ bool LCodeGen::GeneratePrologue() {
   if (info()->IsOptimizing()) {
     ProfileEntryHookStub::MaybeCallEntryHook(masm_);
 
-#ifdef DEBUG
-    if (strlen(FLAG_stop_at) > 0 &&
-        info_->literal()->name()->IsUtf8EqualTo(CStrVector(FLAG_stop_at))) {
-      __ stop("stop_at");
-    }
-#endif
-
     // a1: Callee's JS function.
     // cp: Callee's context.
     // fp: Caller's frame pointer.