Add out-of-line constant pool support to Arm.

src/a64/assembler-a64.h

Index: src/a64/assembler-a64.h
diff --git a/src/a64/assembler-a64.h b/src/a64/assembler-a64.h
index 31d7f17e071612e503c8fbfba88fdf27f1a5b018..43044d49bc88e098a16439b40b3a4e4efa8577fd 100644
--- a/src/a64/assembler-a64.h
+++ b/src/a64/assembler-a64.h
@@ -1790,6 +1790,11 @@ class Assembler : public AssemblerBase {
   // Check if is time to emit a constant pool.
   void CheckConstPool(bool force_emit, bool require_jump);
 
+  // Allocate a constant pool of the correct size for the generated code.
+  MaybeObject* AllocateConstantPool(Heap* heap);
+
+  // Generate the constant pool for the generated code.
+  void PopulateConstantPool(ConstantPoolArray* constant_pool);
 
   // Returns true if we should emit a veneer as soon as possible for a branch
   // which can at most reach to specified pc.