Canonicalize generic types in an isolate specific hash table

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 977ba55040acdc93904c958016db44714e6dce62..3f9830b3c06e680d2c2349e6d26e2f21655821ef 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -771,6 +771,8 @@ class RawTypeArguments : public RawObject {
   // Instantiations leading to bound errors do not get cached.
   RawSmi* length_;
 
+  RawSmi* hash_;
+
   // Variable length data follows here.
   RawAbstractType* const* types() const {
     OPEN_ARRAY_START(RawAbstractType*, RawAbstractType*);
@@ -1687,6 +1689,7 @@ class RawType : public RawAbstractType {
   }
   RawObject* type_class_;  // Either resolved class or unresolved class.
   RawTypeArguments* arguments_;
+  RawSmi* hash_;
   // This type object represents a function type if its signature field is a
   // non-null function object.
   // If this type is malformed or malbounded, the signature field gets
@@ -1728,6 +1731,7 @@ class RawTypeParameter : public RawAbstractType {
   }
   RawClass* parameterized_class_;
   RawString* name_;
+  RawSmi* hash_;
   RawAbstractType* bound_;  // ObjectType if no explicit bound specified.
   RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->bound_); }
   TokenPosition token_pos_;
@@ -1745,6 +1749,7 @@ class RawBoundedType : public RawAbstractType {
   }
   RawAbstractType* type_;
   RawAbstractType* bound_;
+  RawSmi* hash_;
   RawTypeParameter* type_parameter_;  // For more detailed error reporting.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->type_parameter_);
@@ -1760,6 +1765,7 @@ class RawMixinAppType : public RawAbstractType {
     return reinterpret_cast<RawObject**>(&ptr()->super_type_);
   }
   RawAbstractType* super_type_;
+  RawSmi* hash_;
   RawArray* mixin_types_;  // Array of AbstractType.
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&ptr()->mixin_types_);