Refactor FrameAndConstantPoolScope and ConstantPoolUnavailableScope to be architecture independent

src/x64/assembler-x64.h

Index: src/x64/assembler-x64.h
diff --git a/src/x64/assembler-x64.h b/src/x64/assembler-x64.h
index 568719eae473a59d82d23b94a421c63ce8c94da3..9ed3a1de81471295815e0fc844343c316a0f5fbe 100644
--- a/src/x64/assembler-x64.h
+++ b/src/x64/assembler-x64.h
@@ -1123,6 +1123,8 @@ class Assembler : public AssemblerBase {
   // Generate the constant pool for the generated code.
   void PopulateConstantPool(ConstantPoolArray* constant_pool);
 
+  bool is_constant_pool_available() const { return false; }
+
   // Writes a single word of data in the code stream.
   // Used for inline tables, e.g., jump-tables.
   void db(uint8_t data);
@@ -1157,6 +1159,11 @@ class Assembler : public AssemblerBase {
   // Jump near absolute indirect (m64)
   void jmp(const Operand& src);
 
+  void set_constant_pool_available(bool available) {
+    // Constant pool is not supported on x64.
+    UNREACHABLE();
+  }
+
  private:
   byte* addr_at(int pos)  { return buffer_ + pos; }
   uint32_t long_at(int pos)  {
@@ -1571,6 +1578,10 @@ class Assembler : public AssemblerBase {
 
   PositionsRecorder positions_recorder_;
   friend class PositionsRecorder;
+
+  // constant pool
+  friend class FrameAndConstantPoolScope;
+  friend class ConstantPoolUnavailableScope;
 };