Change constant pool marker to be the unconditional, permanently undefined instruction.

src/arm/assembler-arm.h

Index: src/arm/assembler-arm.h
diff --git a/src/arm/assembler-arm.h b/src/arm/assembler-arm.h
index dfcce6011414c363b40db8e96bda4b2208876478..3fab20bcb15734aba17e2406382ba68a603041ab 100644
--- a/src/arm/assembler-arm.h
+++ b/src/arm/assembler-arm.h
@@ -1329,6 +1329,8 @@ class Assembler : public AssemblerBase {
   // and the accessed constant.
   static const int kMaxDistToPool = 4*KB;
   static const int kMaxNumPendingRelocInfo = kMaxDistToPool/kInstrSize;
+  STATIC_ASSERT((kConstantPoolLengthMaxMask & kMaxNumPendingRelocInfo) ==
+                kMaxNumPendingRelocInfo);
 
   // Postpone the generation of the constant pool for the specified number of
   // instructions.