Add IDL and initial Blink API for Background Sync

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index 562aa1cc9017ff92c597bc1b64e3888c913f8974..35e1c27b84975c6498f123b0760e2e78ba314d21 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -60,6 +60,7 @@ class GrContext;
 namespace blink {
 
 class WebAudioBus;
+class WebSyncProvider;
 class WebBlobRegistry;
 class WebBluetooth;
 class WebClipboard;
@@ -654,11 +655,14 @@ public:
 
     virtual WebPushProvider* pushProvider() { return 0; }
 
-
     // navigator.connect --------------------------------------------------

[jkarlin, 2015/02/27 20:08:12]

Double vertical space here seems to be the norm. Add the deleted line back.

 
     virtual WebNavigatorConnectProvider* navigatorConnectProvider() { return 0; }
 
+    // Background Sync API------------------------------------------------------------
+
+    virtual WebSyncProvider* backgroundSyncProvider() { return 0; }
+
 protected:
     BLINK_PLATFORM_EXPORT Platform();
     virtual ~Platform() { }