[interpreter] Move temporary register allocator into own file.

src/interpreter/constant-array-builder.h

Index: src/interpreter/constant-array-builder.h
diff --git a/src/interpreter/constant-array-builder.h b/src/interpreter/constant-array-builder.h
index 12d6f0cebe10c9d52ef777abac55a1994a02d21a..d7e41e377102ced2e9d38341a5d6467770c31cda 100644
--- a/src/interpreter/constant-array-builder.h
+++ b/src/interpreter/constant-array-builder.h
@@ -16,8 +16,11 @@ class Isolate;
 
 namespace interpreter {
 
-// A helper class for constructing constant arrays for the interpreter.
-class ConstantArrayBuilder final : public ZoneObject {
+// A helper class for constructing constant arrays for the
+// interpreter. Each instance of this class is intended to be used to
+// generate exactly one FixedArray of constants via the ToFixedArray
+// method.
+class ConstantArrayBuilder final BASE_EMBEDDED {
  public:
   // Capacity of the 8-bit operand slice.
   static const size_t kLowCapacity = 1u << kBitsPerByte;
@@ -31,7 +34,7 @@ class ConstantArrayBuilder final : public ZoneObject {
   ConstantArrayBuilder(Isolate* isolate, Zone* zone);
 
   // Generate a fixed array of constants based on inserted objects.
-  Handle<FixedArray> ToFixedArray() const;
+  Handle<FixedArray> ToFixedArray();
 
   // Returns the object in the constant pool array that at index
   // |index|.
@@ -83,6 +86,8 @@ class ConstantArrayBuilder final : public ZoneObject {
     DISALLOW_COPY_AND_ASSIGN(ConstantArraySlice);
   };
 
+  IdentityMap<index_t>* constants_map() { return &constants_map_; }
+
   Isolate* isolate_;
   ConstantArraySlice idx8_slice_;
   ConstantArraySlice idx16_slice_;