Fix ConstMethodType.isConstMethodType().

Change-Id: I6f95c8a424b70f51ac2769eb004970c974572fa4
diff --git a/src/main/java/com/android/tools/r8/ir/code/ConstMethodType.java b/src/main/java/com/android/tools/r8/ir/code/ConstMethodType.java
index d258839..fa43dea 100644
--- a/src/main/java/com/android/tools/r8/ir/code/ConstMethodType.java
+++ b/src/main/java/com/android/tools/r8/ir/code/ConstMethodType.java
@@ -80,7 +80,7 @@
   }
 
   @Override
-  public boolean isConstString() {
+  public boolean isConstMethodType() {
     return true;
   }