Don't remove casts to local values.

R=herhut

Change-Id: I24ab7e10669073ea332ee879cef009fc4214ab70
diff --git a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
index e78595d..2cdb1d3 100644
--- a/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
+++ b/src/main/java/com/android/tools/r8/ir/optimize/CodeRewriter.java
@@ -972,6 +972,7 @@
     while (it.hasNext()) {
       Instruction current = it.next();
       if (current.isCheckCast()
+          && current.getLocalInfo() == null
           && current.outValue() != null && current.outValue().isUsed()
           && current.outValue().numberOfPhiUsers() == 0) {
         CheckCast checkCast = current.asCheckCast();