Pepper and WebKit API change to support a plugin knowing if a scrollbar is an overlay one.

third_party/WebKit/Source/WebKit/chromium/src/WebScrollbarImpl.cpp

Index: third_party/WebKit/Source/WebKit/chromium/src/WebScrollbarImpl.cpp
===================================================================
--- third_party/WebKit/Source/WebKit/chromium/src/WebScrollbarImpl.cpp	(revision 91997)
+++ third_party/WebKit/Source/WebKit/chromium/src/WebScrollbarImpl.cpp	(working copy)
@@ -74,6 +74,11 @@
 {
 }
 
+bool WebScrollbarImpl::isOverlay()
+{
+    return m_scrollbar->isOverlayScrollbar();
+}
+
 void WebScrollbarImpl::setLocation(const WebRect& rect)
 {
     IntRect oldRect = m_scrollbar->frameRect();
@@ -344,4 +349,13 @@
     return IntSize();
 }
 
+void WebScrollbarImpl::scrollbarStyleChanged()
+{
+  m_client->overlayChanged(this);
+}
+
+bool WebScrollbarImpl::isOnActivePage() const {
+  return true;
+}
+
 } // namespace WebKit