Issue 5887. Parts must start with 'part of'.

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 a2fd2c447f8d47acb46b9b5857c1d61a6fe1f4d0..e31466f5ff96269d10f5217b6d38041cdcd36536 100644
--- a/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
+++ b/compiler/javatests/com/google/dart/compiler/end2end/inc/MemoryLibrarySource.java
@@ -22,17 +22,20 @@ import java.util.Map;
 public class MemoryLibrarySource implements LibrarySource {
   public static final String IO_EXCEPTION_CONTENT = "simulate-IOException";
   private final String libName;
+  private final Map<String, DartSource> sourceMap;
   private final Map<String, String> sourceContentMap;
   private final Map<String, Long> sourceLastModifiedMap;
 
   public MemoryLibrarySource(String libName) {
     this.libName = libName;
+    sourceMap = Maps.newHashMap();
     sourceContentMap = Maps.newHashMap();
     sourceLastModifiedMap = Maps.newHashMap();
   }
 
   private MemoryLibrarySource(String libName, MemoryLibrarySource parent) {
     this.libName = libName;
+    sourceMap = parent.sourceMap;
     sourceContentMap = parent.sourceContentMap;
     sourceLastModifiedMap = parent.sourceLastModifiedMap;
   }
@@ -75,17 +78,33 @@ public class MemoryLibrarySource implements LibrarySource {
   }
 
   @Override
-  public LibrarySource getImportFor(final String relPath) throws IOException {
+  public LibrarySource getImportFor(String relPath) throws IOException {
+    if (!sourceContentMap.containsKey(relPath)) {
+      return null;
+    }
     return new MemoryLibrarySource(relPath, this);
   }
 
   @Override
   public DartSource getSourceFor(final String relPath) {
+    DartSource result;
+    // check cache
+    {
+      result = sourceMap.get(relPath);
+      if (result != null) {
+        return result;
+      }
+    }
+    // prepare content
     final String content = sourceContentMap.get(relPath);
     final Long sourceLastModified = sourceLastModifiedMap.get(relPath);
+    // may be does not exist
+    if (content == null) {
+      return null;
+    }
     // Return fake UrlDateSource with in-memory content.
     final URI uri = URI.create(relPath);
-    return new UrlDartSource(uri, relPath, this) {
+    result = new UrlDartSource(uri, relPath, this) {
       @Override
       public String getName() {
         return relPath;
@@ -111,12 +130,15 @@ public class MemoryLibrarySource implements LibrarySource {
         return new StringReader(content);
       }
     };
+    sourceMap.put(relPath, result);
+    return result;
   }
 
   /**
    * Sets the given content for the source.
    */
   public void setContent(String relPath, String content) {
+    sourceMap.remove(relPath);
     sourceContentMap.put(relPath, content);
     sourceLastModifiedMap.put(relPath, System.currentTimeMillis());
   }