Revert trunk to version 3.16.4.

src/arm/code-stubs-arm.cc

Index: src/arm/code-stubs-arm.cc
diff --git a/src/arm/code-stubs-arm.cc b/src/arm/code-stubs-arm.cc
index 32173008a3cd209b04025b6945043777ba07f42b..e5c1c3ebd8a068356f9f0bf33d1346a5c0c48d9f 100644
--- a/src/arm/code-stubs-arm.cc
+++ b/src/arm/code-stubs-arm.cc
@@ -6607,11 +6607,6 @@ void StringAddStub::Generate(MacroAssembler* masm) {
   __ tst(r4, Operand(kAsciiDataHintMask));
   __ tst(r5, Operand(kAsciiDataHintMask), ne);
   __ b(ne, &ascii_data);
-  __ eor(r4, r4, Operand(r5));
-  STATIC_ASSERT(kOneByteStringTag != 0 && kAsciiDataHintTag != 0);
-  __ and_(r4, r4, Operand(kOneByteStringTag | kAsciiDataHintTag));
-  __ cmp(r4, Operand(kOneByteStringTag | kAsciiDataHintTag));
-  __ b(eq, &ascii_data);
 
   // Allocate a two byte cons string.
   __ AllocateTwoByteConsString(r7, r6, r4, r5, &call_runtime);