Expose scroll containers via accessibility APIs.

public/web/WebAXObject.h

Index: public/web/WebAXObject.h
diff --git a/public/web/WebAXObject.h b/public/web/WebAXObject.h
index cd5b27b14bc25f409392eff255cc1eeba2fb93c8..e9a7813b3538b7b5d70d89cc28b03d33805e1312 100644
--- a/public/web/WebAXObject.h
+++ b/public/web/WebAXObject.h
@@ -32,6 +32,7 @@
 #define WebAXObject_h
 
 #include "../platform/WebCommon.h"
+#include "../platform/WebPoint.h"
 #include "../platform/WebPrivatePtr.h"
 #include "../platform/WebVector.h"
 #include "WebAXEnums.h"
@@ -283,6 +284,13 @@ public:
     BLINK_EXPORT void characterOffsets(WebVector<int>&) const;
     BLINK_EXPORT void wordBoundaries(WebVector<int>& starts, WebVector<int>& ends) const;
 
+    // Scrollable containers.
+    BLINK_EXPORT bool isScrollableContainer() const;
+    BLINK_EXPORT WebPoint scrollOffset() const;
+    BLINK_EXPORT WebPoint minimumScrollOffset() const;
+    BLINK_EXPORT WebPoint maximumScrollOffset() const;
+    BLINK_EXPORT void setScrollOffset(const WebPoint&) const;
+
     // Make this object visible by scrolling as many nested scrollable views as needed.
     BLINK_EXPORT void scrollToMakeVisible() const;
     // Same, but if the whole object can't be made visible, try for this subrect, in local coordinates.