Reapply "Move isolate loading to a separate loader isolate."

Source/bindings/dart/DartUtilities.cpp

Index: Source/bindings/dart/DartUtilities.cpp
diff --git a/Source/bindings/dart/DartUtilities.cpp b/Source/bindings/dart/DartUtilities.cpp
index dfa636ea1a4c963f4f3a190ae08181a1e34fbc6f..99508573306e3ed8719d254eee05ae6a70c5c86c 100644
--- a/Source/bindings/dart/DartUtilities.cpp
+++ b/Source/bindings/dart/DartUtilities.cpp
@@ -941,6 +941,46 @@ const uint8_t* DartUtilities::fullSnapshot(Frame* frame)
     return reinterpret_cast<uint8_t*>(snapshotData.data());
 }
 
+Dart_Handle DartUtilities::canonicalizeUrl(Dart_Handle library, Dart_Handle urlHandle, String url)
+{
+    if (url.startsWith("dart:") || url.startsWith("package:"))
+        return urlHandle;
+
+    Dart_Handle libraryURLHandle = Dart_LibraryUrl(library);
+    ASSERT(!Dart_IsError(libraryURLHandle));
+    String libraryURL = DartUtilities::toString(libraryURLHandle);
+
+    bool packageScheme = false;
+
+    const char* kPackagePrefix = "package:";
+    const int kPackagePrefixLength = strlen(kPackagePrefix);
+
+    const char* kHttpPrefix = "http://";
+    const int kHttpPrefixLength = strlen(kHttpPrefix);
+
+    if (libraryURL.startsWith(kPackagePrefix)) {
+        // KURL has problems concating package:foo/bar (without slashes right after colon)
+        // and relative urls. Therefore pretend to be a standard absolute URL.
+        packageScheme = true;
+        libraryURL = kHttpPrefix + libraryURL.substring(kPackagePrefixLength);
+    }
+
+    const KURL canonical = KURL(KURL(KURL(), libraryURL), url);
+    String result = canonical.string();
+    if (packageScheme)
+        result = kPackagePrefix + result.substring(kHttpPrefixLength);
+    return DartUtilities::stringToDartString(result);
+}
+
+void DartUtilities::reportProblem(ScriptExecutionContext* context, const String& error)
+{
+    String sourceURL = context->url().string();
+    // FIXME: Pass in line number and stack trace.
+    if (context && context->isDocument()) {
+        static_cast<Document*>(context)->reportException(ErrorEvent::create(error, sourceURL, 0, 0), 0, NotSharableCrossOrigin);
+    }
+}
+
 void DartUtilities::reportProblem(ScriptExecutionContext* context, Dart_Handle result)
 {
     // FIXME: provide sourceURL.