Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/core/frame/FrameView.cpp

Index: third_party/WebKit/Source/core/frame/FrameView.cpp
diff --git a/third_party/WebKit/Source/core/frame/FrameView.cpp b/third_party/WebKit/Source/core/frame/FrameView.cpp
index 44f2446632fc84ee790b38e7d3a2133f1022b82c..0cb8bdca2d84e53a4fd50949f517b68bf719eb19 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -3309,6 +3309,23 @@ IntSize FrameView::contentsSize() const
     return m_contentsSize;
 }
 
+IntRect FrameView::visibleContentRectForPainting() const
+{
+    if (m_visibleContentRectForPainting)
+        return *m_visibleContentRectForPainting;
+    return visibleContentRect();
+}
+
+void FrameView::setVisibleContentRectForPainting(const IntRect& rect)
+{
+    m_visibleContentRectForPainting = IntRect(rect);
+}
+
+void FrameView::resetVisibleContentRectForPainting()
+{
+    m_visibleContentRectForPainting = WTF::nullopt;
+}
+
 IntPoint FrameView::minimumScrollPosition() const
 {
     return IntPoint(-scrollOrigin().x(), -scrollOrigin().y());
@@ -3387,7 +3404,7 @@ void FrameView::setScrollOffset(const DoublePoint& offset, ScrollType scrollType
         cache->handleScrollPositionChanged(this);
 
     frame().loader().saveScrollState();
-    frame().loader().client()->didChangeScrollOffset();
+    didChangeScrollOffset();
 
     if (scrollType == CompositorScroll && m_frame->isMainFrame()) {
         if (DocumentLoader* documentLoader = m_frame->loader().documentLoader())
@@ -3398,6 +3415,13 @@ void FrameView::setScrollOffset(const DoublePoint& offset, ScrollType scrollType
         clearScrollAnchor();
 }
 
+void FrameView::didChangeScrollOffset()
+{
+    frame().loader().client()->didChangeScrollOffset();
+    if (frame().isMainFrame())
+        frame().host()->chromeClient().mainFrameScrollOffsetChanged();
+}
+
 void FrameView::clearScrollAnchor()
 {
     if (!RuntimeEnabledFeatures::scrollAnchoringEnabled())