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 50137729160c42130d6a2ec3d239691f308eca76..0d0dd6d12df512a531436e8cd3290bf4e6422997 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -3367,6 +3367,13 @@ IntSize FrameView::contentsSize() const
     return m_contentsSize;
 }
 
+void FrameView::clipPaintRect(FloatRect* paintRect) const
+{
+    paintRect->intersect(
+        page()->chromeClient().visibleContentRectForPainting().value_or(
+            visibleContentRect()));
+}
+
 IntPoint FrameView::minimumScrollPosition() const
 {
     return IntPoint(-scrollOrigin().x(), -scrollOrigin().y());
@@ -3445,7 +3452,7 @@ 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())
@@ -3456,6 +3463,13 @@ 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())