Support [TypeChecking] on dependent/partial interfaces.

Source/bindings/tests/idls/core/TestPartialInterface4.idl

Index: Source/bindings/tests/idls/core/TestPartialInterface4.idl
diff --git a/Source/core/html/canvas/WebGLSampler.idl b/Source/bindings/tests/idls/core/TestPartialInterface4.idl
similarity index 56%
copy from Source/core/html/canvas/WebGLSampler.idl
copy to Source/bindings/tests/idls/core/TestPartialInterface4.idl
index 565f3d6d97129db07ba3aa91d5be51dd8051608f..a28b51500b1952b103772e8770b5408328a89b5c 100644
--- a/Source/core/html/canvas/WebGLSampler.idl
+++ b/Source/bindings/tests/idls/core/TestPartialInterface4.idl
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 [
-    RuntimeEnabled=UnsafeES3APIs,
-    WillBeGarbageCollected
-] interface WebGLSampler {
-};
+    TypeChecking=Interface,

[haraken, 2015/02/21 22:39:48]

Just to confirm: This affects methods/attributes of TestPartialInterface4 but
doesn't affect methods/attributes of TestInterfaceDocument, right?

[sof, 2015/02/22 14:05:16]

Correct. I've altered the partial interface to make verifying that easier.

Also noticed that the merging of these attributes was a bit
unexpected&surprising: the interface-level extended attribute value would
override and replace any local ones. To continue this "principle of least
astonishment"-like effort if nothing else, I tidied that up. pta(nother)l?

+] partial interface TestInterfaceDocument {
+    static void voidMethodDocument(Document document);
+};