Make -printusage format compatible with ProGuard

The resulting file was missing ":" after class names
in the case where member names were printed for that class.

Bug: b/138361224
Change-Id: I64c0275e029d9bf7d22d3133aefa725b1328b6e2
diff --git a/src/main/java/com/android/tools/r8/shaking/UsagePrinter.java b/src/main/java/com/android/tools/r8/shaking/UsagePrinter.java
index 132da90..c224dbd 100644
--- a/src/main/java/com/android/tools/r8/shaking/UsagePrinter.java
+++ b/src/main/java/com/android/tools/r8/shaking/UsagePrinter.java
@@ -51,6 +51,7 @@
     assert enclosingClazz != null;
     if (!clazzPrefixPrinted) {
       writer.append(enclosingClazz.toSourceString());
+      writer.append(':');
       writer.append(StringUtils.LINE_SEPARATOR);
       clazzPrefixPrinted = true;
     }
diff --git a/src/test/java/com/android/tools/r8/shaking/PrintUsageTest.java b/src/test/java/com/android/tools/r8/shaking/PrintUsageTest.java
index 8247e92..e4bd7c8 100644
--- a/src/test/java/com/android/tools/r8/shaking/PrintUsageTest.java
+++ b/src/test/java/com/android/tools/r8/shaking/PrintUsageTest.java
@@ -202,6 +202,10 @@
     private ClassSubject lastClazz = null;
 
     private void readClazz(String line) {
+      int length = line.length();
+      if (line.charAt(length - 1) == ':') {
+        line = line.substring(0, length - 1);
+      }
       if (printedUsage.containsKey(line)) {
         lastClazz = printedUsage.get(line);
       } else {