Bug 942631 part 4. Allow WebIDL attributes to return a sequence if it's cached. r=peterv

dom/bindings/parser/WebIDL.py

@@ -2652,9 +2652,9 @@ class IDLAttribute(IDLInterfaceMember):
         if self.type.isDictionary():
             raise WebIDLError("An attribute cannot be of a dictionary type",
                               [self.location])
-        if self.type.isSequence():
-            raise WebIDLError("An attribute cannot be of a sequence type",
-                              [self.location])
+        if self.type.isSequence() and not self.getExtendedAttribute("Cached"):
+            raise WebIDLError("A non-cached attribute cannot be of a sequence "
+                              "type", [self.location])
         if self.type.isUnion():
             for f in self.type.unroll().flatMemberTypes:
                 if f.isDictionary():

dom/bindings/test/TestBindingHeader.h

@@ -340,6 +340,7 @@ public:
   void PassConsequentialInterface(IndirectlyImplementedInterface&);
 
   // Sequence types
+  void GetReadonlySequence(nsTArray<int32_t>&);
   void ReceiveSequence(nsTArray<int32_t>&);
   void ReceiveNullableSequence(Nullable< nsTArray<int32_t> >&);
   void ReceiveSequenceOfNullableInts(nsTArray< Nullable<int32_t> >&);

dom/bindings/test/TestCodeGen.webidl

@@ -295,6 +295,8 @@ interface TestInterface {
   void passConsequentialInterface(IndirectlyImplementedInterface arg);
 
   // Sequence types
+  [Cached, Pure]
+  readonly attribute sequence<long> readonlySequence;
   sequence<long> receiveSequence();
   sequence<long>? receiveNullableSequence();
   sequence<long?> receiveSequenceOfNullableInts();

dom/bindings/test/TestExampleGen.webidl

@@ -191,6 +191,8 @@ interface TestExampleInterface {
   void passConsequentialInterface(IndirectlyImplementedInterface arg);
 
   // Sequence types
+  [Cached, Pure]
+  readonly attribute sequence<long> readonlySequence;
   sequence<long> receiveSequence();
   sequence<long>? receiveNullableSequence();
   sequence<long?> receiveSequenceOfNullableInts();

dom/bindings/test/TestJSImplGen.webidl

@@ -212,6 +212,8 @@ interface TestJSImplInterface {
   void passConsequentialInterface(IndirectlyImplementedInterface arg);
 
   // Sequence types
+  [Cached, Pure]
+  readonly attribute sequence<long> readonlySequence;
   sequence<long> receiveSequence();
   sequence<long>? receiveNullableSequence();
   sequence<long?> receiveSequenceOfNullableInts();