Incorporating review feedback from https://codereview.chromium.org/24294002/

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 14d39b04c9395cc720d8a8f5b830cd2ed8bc5064..d05656dfe0f29a8846aa2622479cda608cbbae5f 100644
--- a/Source/bindings/dart/DartUtilities.cpp
+++ b/Source/bindings/dart/DartUtilities.cpp
@@ -30,6 +30,9 @@
 #include "config.h"
 #include "bindings/dart/DartUtilities.h"
 
+#include "DartBlob.h"
+#include "DartIDBKeyRange.h"
+#include "DartImageData.h"
 #include "DartMessagePort.h"
 #include "bindings/dart/DartDOMData.h"
 #include "bindings/dart/DartHandleProxy.h"
@@ -346,17 +349,28 @@ bool DartUtilities::isDateTime(Dart_Handle handle)
 
 bool DartUtilities::isBlob(Dart_Handle handle)
 {
-    return objectIsType(handle, htmlLibraryName, "Blob");
+    return objectIsClass(handle, DartDOMWrapper::dartClass<DartBlob>());
 }
 
 bool DartUtilities::isImageData(Dart_Handle handle)
 {
-    return objectIsType(handle, htmlLibraryName, "ImageData");
+    return objectIsClass(handle, DartDOMWrapper::dartClass<DartImageData>());
 }
 
 bool DartUtilities::isIDBKeyRange(Dart_Handle handle)
 {
-    return objectIsType(handle, indexedDBLibraryName, "KeyRange");
+    return objectIsClass(handle, DartDOMWrapper::dartClass<DartIDBKeyRange>());
+}
+
+bool DartUtilities::objectIsClass(Dart_Handle handle, Dart_Handle cls)
+{
+    bool isType = false;
+    Dart_Handle result = Dart_ObjectIsType(handle, cls, &isType);
+    ASSERT(!Dart_IsError(result));
+    if (Dart_IsError(result))
+        return false;
+
+    return isType;
 }
 
 bool DartUtilities::objectIsType(Dart_Handle handle, const char* libraryName, const char* typeName)