diff --git a/content/canvas/test/test_canvas.html b/content/canvas/test/test_canvas.html
index 967024618076..22e357e475c9 100644
--- a/content/canvas/test/test_canvas.html
+++ b/content/canvas/test/test_canvas.html
@@ -3538,8 +3538,13 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.drawImage(null, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
 
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 }
 </script>
@@ -3715,17 +3720,39 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.drawImage(undefined, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e }; 
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 var _thrown = undefined; try {
   ctx.drawImage(0, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 var _thrown = undefined; try {
   ctx.drawImage("", 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 var _thrown = undefined; try {
   ctx.drawImage(document.createElement('p'), 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
-
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 }
 </script>
@@ -7696,7 +7723,12 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.createImageData(null);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown instanceof TypeError, "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 
 }
@@ -9207,8 +9239,12 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.putImageData(null, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
-
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 }
 </script>
@@ -9319,13 +9355,31 @@ var ctx = canvas.getContext('2d');
 var imgdata = { width: 1, height: 1, data: [255, 0, 0, 255] };
 var _thrown = undefined; try {
   ctx.putImageData(imgdata, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e }; 
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 var _thrown = undefined; try {
   ctx.putImageData("cheese", 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 var _thrown = undefined; try {
   ctx.putImageData(42, 0, 0);
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
+
 
 
 }
@@ -15131,7 +15185,12 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.createPattern(null, 'repeat');
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 
 }
@@ -15150,7 +15209,12 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.createPattern('image_red.png', 'repeat');
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 
 }
@@ -15169,7 +15233,12 @@ var ctx = canvas.getContext('2d');
 
 var _thrown = undefined; try {
   ctx.createPattern(undefined, 'repeat');
-} catch (e) { _thrown = e }; todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} catch (e) { _thrown = e };
+if (IsAzureEnabled()) {
+  ok(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+} else {
+  todo(_thrown && _thrown.name == "TypeError", "should throw TypeError");
+}
 
 
 }
diff --git a/dom/bindings/Codegen.py b/dom/bindings/Codegen.py
index 397f748f9a60..f8a0ffbcbf65 100644
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@@ -1513,13 +1513,16 @@ def getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
     # Also, we should not have a defaultValue if we know we're an object
     assert(not isDefinitelyObject or defaultValue is None)
 
-    # A helper function for dealing with failures due to the JS value being the
+    # Helper functions for dealing with failures due to the JS value being the
     # wrong type of value
-    def onFailure(failureCode, isWorker):
+    def onFailureNotAnObject(failureCode):
         return CGWrapper(CGGeneric(
                 failureCode or
-                "return Throw<%s>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);"
-                % toStringBool(isWorker)), post="\n")
+                'return ThrowErrorMessage(cx, MSG_NOT_OBJECT);'), post="\n")
+    def onFailureBadType(failureCode, typeName):
+        return CGWrapper(CGGeneric(
+                failureCode or
+                'return ThrowErrorMessage(cx, MSG_DOES_NOT_IMPLEMENT_INTERFACE, "%s");' % typeName), post="\n")
 
     # A helper function for handling default values.  Takes a template
     # body and the C++ code to set the default value and wraps the
@@ -1547,7 +1550,7 @@ def getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
     # A helper function for wrapping up the template body for
     # possibly-nullable objecty stuff
     def wrapObjectTemplate(templateBody, isDefinitelyObject, type,
-                           codeToSetNull, isWorker, failureCode=None):
+                           codeToSetNull, failureCode=None):
         if not isDefinitelyObject:
             # Handle the non-object cases by wrapping up the whole
             # thing in an if cascade.
@@ -1560,7 +1563,7 @@ def getJSToNativeConversionTemplate(type, descriptorProvider, failureCode=None,
                     "  %s;\n" % codeToSetNull)
             templateBody += (
                 "} else {\n" +
-                CGIndenter(onFailure(failureCode, isWorker)).define() +
+                CGIndenter(onFailureNotAnObject(failureCode)).define() +
                 "}")
             if type.nullable():
                 templateBody = handleDefaultNull(templateBody, codeToSetNull)
@@ -1646,8 +1649,7 @@ for (uint32_t i = 0; i < length; ++i) {
         templateBody += "\n}"
         templateBody = wrapObjectTemplate(templateBody, isDefinitelyObject,
                                           type,
-                                          "const_cast< %s & >(${declName}).SetNull()" % mutableTypeName.define(),
-                                          descriptorProvider.workers)
+                                          "const_cast< %s & >(${declName}).SetNull()" % mutableTypeName.define())
         return (templateBody, typeName, None, isOptional)
 
     if type.isUnion():
@@ -1666,6 +1668,7 @@ for (uint32_t i = 0; i < length; ++i) {
             unionArgumentObj += ".ref()"
 
         memberTypes = type.flatMemberTypes
+        names = []
 
         interfaceMemberTypes = filter(lambda t: t.isNonCallbackInterface(), memberTypes)
         if len(interfaceMemberTypes) > 0:
@@ -1676,6 +1679,7 @@ for (uint32_t i = 0; i < length; ++i) {
                 else:
                     name = memberType.name
                 interfaceObject.append(CGGeneric("(failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext" % (unionArgumentObj, name)))
+                names.append(name)
             interfaceObject = CGWrapper(CGList(interfaceObject, " ||\n"), pre="done = ", post=";\n", reindent=True)
         else:
             interfaceObject = None
@@ -1692,6 +1696,7 @@ for (uint32_t i = 0; i < length; ++i) {
             arrayObject = CGWrapper(CGIndenter(arrayObject),
                                     pre="if (IsArrayLike(cx, &argObj)) {\n",
                                     post="}")
+            names.append(name)
         else:
             arrayObject = None
 
@@ -1705,6 +1710,7 @@ for (uint32_t i = 0; i < length; ++i) {
             dateObject = CGWrapper(CGIndenter(dateObject),
                                    pre="if (JS_ObjectIsDate(cx, &argObj)) {\n",
                                    post="\n}")
+            names.append(name)
         else:
             dateObject = None
 
@@ -1714,6 +1720,7 @@ for (uint32_t i = 0; i < length; ++i) {
             memberType = callbackMemberTypes[0]
             name = memberType.name
             callbackObject = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
+            names.append(name)
         else:
             callbackObject = None
 
@@ -1783,6 +1790,7 @@ for (uint32_t i = 0; i < length; ++i) {
             else:
                 name = memberType.name
             other = CGGeneric("done = (failed = !%s.TrySetTo%s(cx, ${val}, ${valPtr}, tryNext)) || !tryNext;" % (unionArgumentObj, name))
+            names.append(name)
             if hasObjectTypes:
                 other = CGWrapper(CGIndenter(other), "{\n", post="\n}")
                 if object:
@@ -1799,8 +1807,8 @@ for (uint32_t i = 0; i < length; ++i) {
                           "  return false;\n"
                           "}\n"
                           "if (!done) {\n"
-                          "  return Throw<%s>(cx, NS_ERROR_XPC_BAD_CONVERT_JS);\n"
-                          "}" % toStringBool(descriptorProvider.workers))
+                          "  return ThrowErrorMessage(cx, MSG_NOT_IN_UNION, \"%s\");\n"
+                          "}" % ", ".join(names))
         templateBody = CGWrapper(CGIndenter(CGList([templateBody, throw], "\n")), pre="{\n", post="\n}")
 
         typeName = type.name
@@ -1939,8 +1947,8 @@ for (uint32_t i = 0; i < length; ++i) {
                 "jsval tmpVal = ${val};\n" +
                 typePtr + " tmp;\n"
                 "if (NS_FAILED(xpc_qsUnwrapArg<" + typeName + ">(cx, ${val}, &tmp, static_cast<" + typeName + "**>(getter_AddRefs(${holderName})), &tmpVal))) {\n")
-            templateBody += CGIndenter(onFailure(failureCode,
-                                                 descriptor.workers)).define()
+            templateBody += CGIndenter(onFailureBadType(failureCode,
+                                                        descriptor.interface.identifier.name)).define()
             templateBody += ("}\n"
                 "MOZ_ASSERT(tmp);\n")
 
@@ -1959,7 +1967,7 @@ for (uint32_t i = 0; i < length; ++i) {
 
         templateBody = wrapObjectTemplate(templateBody, isDefinitelyObject,
                                           type, "${declName} = NULL",
-                                          descriptor.workers, failureCode)
+                                          failureCode)
 
         declType = CGGeneric(declType)
         if holderType is not None:
@@ -1997,10 +2005,10 @@ for (uint32_t i = 0; i < length; ++i) {
         template = (
             "%s.%s(cx, &${val}.toObject());\n"
             "if (!%s.%s().inited()) {\n"
-            "%s" # No newline here because onFailure() handles that
+            "%s" # No newline here because onFailureBadType() handles that
             "}\n" %
             (constructLoc, constructMethod, constructLoc, constructInternal,
-             CGIndenter(onFailure(failureCode, descriptorProvider.workers)).define()))
+             CGIndenter(onFailureBadType(failureCode, type.name)).define()))
         nullableTarget = ""
         if type.nullable():
             if isOptional:
@@ -2014,7 +2022,6 @@ for (uint32_t i = 0; i < length; ++i) {
             template += "${declName} = ${holderName}.addr();"
         template = wrapObjectTemplate(template, isDefinitelyObject, type,
                                       "%s = NULL" % nullableTarget,
-                                      descriptorProvider.workers,
                                       failureCode)
 
         if holderType is not None:
@@ -2148,7 +2155,7 @@ for (uint32_t i = 0; i < length; ++i) {
         template = wrapObjectTemplate("${declName} = &${val}.toObject();",
                                       isDefinitelyObject, type,
                                       "${declName} = NULL",
-                                      descriptorProvider.workers, failureCode)
+                                      failureCode)
         if type.nullable():
             declType = CGGeneric("JSObject*")
         else:
diff --git a/dom/bindings/Errors.msg b/dom/bindings/Errors.msg
index a4f7a1e841b7..0ce10da33857 100644
--- a/dom/bindings/Errors.msg
+++ b/dom/bindings/Errors.msg
@@ -19,5 +19,8 @@
  * be replaced with a string value when the error is reported.
  */
 
-MSG_DEF(MSG_INVALID_ENUM_VALUE, 2, "Value '{0}' is not a valid value for enumeration '{1}'.")
+MSG_DEF(MSG_INVALID_ENUM_VALUE, 2, "Value '{0}' is not a valid value for enumeration {1}.")
 MSG_DEF(MSG_MISSING_ARGUMENTS, 1, "Not enough arguments to {0}.")
+MSG_DEF(MSG_NOT_OBJECT, 0, "Value not an object.")
+MSG_DEF(MSG_DOES_NOT_IMPLEMENT_INTERFACE, 1, "Value does not implement interface {0}.")
+MSG_DEF(MSG_NOT_IN_UNION, 1, "Value could not be converted to any of: {0}.")