Remove FixturePreparer.Extend()

Use GroupFixturePreparers instead.

Bug: 182885307
Test: m nothing
Change-Id: Idc01d3cc5a57576a4cf417e9105d1ab851126e10
diff --git a/android/fixture.go b/android/fixture.go
index 883647c..5fc668a 100644
--- a/android/fixture.go
+++ b/android/fixture.go
@@ -367,15 +367,6 @@
 	// Return the flattened and deduped list of simpleFixturePreparer pointers.
 	list() []*simpleFixturePreparer
 
-	// Creates a copy of this instance and adds some additional preparers.
-	//
-	// Before the preparers are used they are combined with the current preparer, any groups of
-	// preparers are flattened, and the list is deduped so that each preparer is only used once. See
-	// the file documentation in android/fixture.go for more details.
-	//
-	// deprecated: Use GroupFixturePreparers() instead.
-	Extend(preparers ...FixturePreparer) FixturePreparer
-
 	// Create a Fixture.
 	Fixture(t *testing.T) Fixture
 
@@ -656,17 +647,12 @@
 	b.self = self
 }
 
-func (b *baseFixturePreparer) Extend(preparers ...FixturePreparer) FixturePreparer {
-	all := dedupAndFlattenPreparers(b.self.list(), preparers)
-	return newFixturePreparer(all)
-}
-
 func (b *baseFixturePreparer) Fixture(t *testing.T) Fixture {
 	return createFixture(t, t.TempDir(), b.self.list())
 }
 
 func (b *baseFixturePreparer) ExtendWithErrorHandler(errorHandler FixtureErrorHandler) FixturePreparer {
-	return b.self.Extend(newSimpleFixturePreparer(func(fixture *fixture) {
+	return GroupFixturePreparers(b.self, newSimpleFixturePreparer(func(fixture *fixture) {
 		fixture.errorHandler = errorHandler
 	}))
 }
diff --git a/android/fixture_test.go b/android/fixture_test.go
index 8f04715..5b810e0 100644
--- a/android/fixture_test.go
+++ b/android/fixture_test.go
@@ -41,7 +41,7 @@
 
 	group := GroupFixturePreparers(preparer1, preparer2, preparer1, preparer1Then2)
 
-	extension := group.Extend(preparer4, preparer2)
+	extension := GroupFixturePreparers(group, preparer4, preparer2)
 
 	GroupFixturePreparers(extension, preparer1, preparer2, preparer2Then1, preparer3).Fixture(t)