Issue 3123. Catch exceptions in Source.exists()/initProperties()

compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java

Index: compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
diff --git a/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java b/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
index 8b221e725d40f6c99e65ec3f2b427cda4e83d1b7..4d7aa25052ce004b1c44e62c1ea17d923fa7a6f7 100644
--- a/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
+++ b/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
@@ -80,7 +80,7 @@ public class MemoryLibrarySource implements LibrarySource {
     final String content = sourceContentMap.get(relPath);
     final Long sourceLastModified = sourceLastModifiedMap.get(relPath);
     // Return fake UrlDateSource with in-memory content.
-    URI uri = URI.create(relPath);
+    final URI uri = URI.create(relPath);
     return new UrlDartSource(uri, relPath, this) {
       @Override
       public String getName() {
@@ -88,6 +88,11 @@ public class MemoryLibrarySource implements LibrarySource {
       }
 
       @Override
+      public URI getUri() {
+        return uri;
+      }
+
+      @Override
       public boolean exists() {
         return content != null;
       }