Add IDL and initial Blink API for Background Sync

Source/modules/background_sync/ServiceWorkerGlobalScopeSync.idl

Index: Source/modules/background_sync/ServiceWorkerGlobalScopeSync.idl
diff --git a/Source/core/timing/ConsoleMemory.idl b/Source/modules/background_sync/ServiceWorkerGlobalScopeSync.idl
similarity index 59%
copy from Source/core/timing/ConsoleMemory.idl
copy to Source/modules/background_sync/ServiceWorkerGlobalScopeSync.idl
index bdd31e20383d592a38ab1140ee9328a59fd7dbd2..0860b81a5aba486b2de423eb1f3dbf6d5a6a4940 100644
--- a/Source/core/timing/ConsoleMemory.idl
+++ b/Source/modules/background_sync/ServiceWorkerGlobalScopeSync.idl
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 
 [

[Michael van Ouwerkerk, 2015/03/02 14:19:11]

nit: add a link to the editor's draft section that defines this idl. Same for
all the other idl files.

-    ImplementedAs=ConsoleMemory,
-] partial interface Console {
-    readonly attribute MemoryInfo memory;
+    RuntimeEnabled=BackgroundSync,
+] partial interface ServiceWorkerGlobalScope {
+    attribute EventHandler onsync;
 };