Issue 1548. If URI can not be parsed, return null.

compiler/java/com/google/dart/compiler/DartCompiler.java

Index: compiler/java/com/google/dart/compiler/DartCompiler.java
diff --git a/compiler/java/com/google/dart/compiler/DartCompiler.java b/compiler/java/com/google/dart/compiler/DartCompiler.java
index 8dd9e722ac0f124ae08f0b49456b9b8fa4562da0..73b78054a27a83389642c223aea568f9a5858afb 100644
--- a/compiler/java/com/google/dart/compiler/DartCompiler.java
+++ b/compiler/java/com/google/dart/compiler/DartCompiler.java
@@ -110,12 +110,12 @@ public class DartCompiler {
 
     @Override
     public LibrarySource getImportFor(String relPath) {
-      throw new AssertionError();
+      return null;
     }
 
     @Override
     public DartSource getSourceFor(String relPath) {
-      throw new AssertionError();
+      return null;
     }
   }
 
@@ -249,13 +249,10 @@ public class DartCompiler {
             final DartSource dartSrc = libSrc.getSourceFor(relPath);
             if (dartSrc == null || !dartSrc.exists()) {
               // Dart Editor needs to have all missing files reported as compilation errors.
-              // In addition, continue allows lib.populateTopLevelNodes() to be called so that the
-              // top level elements are populated preventing an NPE later on.
               reportMissingSource(context, libSrc, libNode);
               continue;
             }
 
-
             if (!incremental
                 || (libIsDartUri && !usePrecompiledDartLibs)
                 || isSourceOutOfDate(dartSrc, libSrc)) {
@@ -407,12 +404,7 @@ public class DartCompiler {
           if (SystemLibraryManager.isDartSpec(libSpec)) {
             dep = context.getSystemLibraryFor(libSpec);
           } else {
-            try {
-              dep = libSrc.getImportFor(libSpec);
-            } catch (IllegalArgumentException ex) {
-              reportImportError(context, libSrc, libNode);
-              continue;
-            }
+            dep = libSrc.getImportFor(libSpec);
           }
           if (dep == null || !dep.exists()) {
             reportMissingSource(context, libSrc, libNode);
@@ -883,15 +875,6 @@ public class DartCompiler {
       event.setSource(libSrc);
       context.onError(event);
     }
-
-    private void reportImportError(DartCompilerContext context,
-                                   LibrarySource libSrc,
-                                   LibraryNode libNode) {
-      DartCompilationError event = new DartCompilationError(libNode,
-          DartCompilerErrorCode.COULD_NOT_PARSE_IMPORT, libNode.getText());
-      event.setSource(libSrc);
-      context.onError(event);
-    }
     CoreTypeProvider getTypeProvider() {
       typeProvider.getClass(); // Quick null check.
       return typeProvider;