Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 4b444f9b9237fa328f1dcbec4003f9b4d6c1f077..ec8c621bbb8bad0fb8193589a9b1f6a46e7acc91 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -393,7 +393,7 @@ bool ScrollingCoordinator::scrollableAreaScrollLayerDidChange(ScrollableArea* sc
     WebLayer* containerLayer = toWebLayer(scrollableArea->layerForContainer());
     if (webLayer) {
         webLayer->setScrollClipLayer(containerLayer);
-        DoublePoint scrollPosition(scrollableArea->scrollPositionDouble() - scrollableArea->minimumScrollPositionDouble());
+        DoublePoint scrollPosition(scrollableArea->scrollPositionDouble() + scrollableArea->scrollOrigin());
         webLayer->setScrollPositionDouble(scrollPosition);
 
         webLayer->setBounds(scrollableArea->contentsSize());
@@ -671,6 +671,7 @@ void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainTh
     if (!m_page->mainFrame()->isLocalFrame() || !m_page->deprecatedLocalMainFrame()->view())
         return;
 
+    WebLayer* visualViewportScrollLayer = toWebLayer(m_page->frameHost().visualViewport().scrollLayer());
     GraphicsLayer* layer = m_page->deprecatedLocalMainFrame()->view()->layerForScrolling();
     if (WebLayer* scrollLayer = toWebLayer(layer)) {
         m_lastMainThreadScrollingReasons = mainThreadScrollingReasons;
@@ -680,12 +681,16 @@ void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainTh
                 scrollAnimator->takeOverCompositorAnimation();
             }
             scrollLayer->addMainThreadScrollingReasons(mainThreadScrollingReasons);
+            if (visualViewportScrollLayer)
+                visualViewportScrollLayer->addMainThreadScrollingReasons(mainThreadScrollingReasons);
         } else {
             // Clear all main thread scrolling reasons except the one that's set
             // if there is a running scroll animation.
             uint32_t mainThreadScrollingReasonsToClear = ~0u;
             mainThreadScrollingReasonsToClear &= ~MainThreadScrollingReason::kAnimatingScrollOnMainThread;
             scrollLayer->clearMainThreadScrollingReasons(mainThreadScrollingReasonsToClear);
+            if (visualViewportScrollLayer)
+                visualViewportScrollLayer->clearMainThreadScrollingReasons(mainThreadScrollingReasonsToClear);
         }
     }
 }