Bigtable: Add support for Table-level IAM.

Changes to address bug 117902632.

Change-Id: I0cc38a6103b32f36cc7e93cb4e7db857427b5dd0
Reviewed-on: https://code-review.googlesource.com/c/gocloud/+/44590
Reviewed-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Igor Bernstein <igorbernstein@google.com>
diff --git a/bigtable/admin.go b/bigtable/admin.go
index 9404158..e1e4bb2 100644
--- a/bigtable/admin.go
+++ b/bigtable/admin.go
@@ -977,7 +977,12 @@
 // InstanceIAM returns the instance's IAM handle.
 func (iac *InstanceAdminClient) InstanceIAM(instanceID string) *iam.Handle {
 	return iam.InternalNewHandleGRPCClient(iac.iClient, "projects/"+iac.project+"/instances/"+instanceID)
+}
 
+// TableIAM creates an IAM client specific to a given Instance and Table within the configured project.
+func (iac *InstanceAdminClient) TableIAM(instanceID, tableID string) *iam.Handle {
+	return iam.InternalNewHandleGRPCClient(iac.iClient,
+		"projects/"+iac.project+"/instances/"+instanceID+"/tables/"+tableID)
 }
 
 // Routing policies.