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..b3945d6e4b50aed6850ba77ebfcc7475d0485c90 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.cpp
+++ b/third_party/WebKit/Source/core/frame/FrameView.cpp
@@ -158,6 +158,7 @@ FrameView::FrameView(LocalFrame* frame)
     , m_verticalScrollbarMode(ScrollbarAuto)
     , m_horizontalScrollbarLock(false)
     , m_verticalScrollbarLock(false)
+    , m_visibleContentRectForRecording(nullptr)
     , m_scrollbarsAvoidingResizer(0)
     , m_scrollbarsSuppressed(false)
     , m_inUpdateScrollbars(false)
@@ -3309,6 +3310,28 @@ IntSize FrameView::contentsSize() const
     return m_contentsSize;
 }
 
+IntSize FrameView::visibleContentSizeForRecording() const
+{
+    return visibleContentRectForRecording().size();
+}
+
+IntRect FrameView::visibleContentRectForRecording() const
+{
+    if (m_visibleContentRectForRecording)
+        return *m_visibleContentRectForRecording;
+    return visibleContentRect();
+}
+
+void FrameView::setVisibleContentRectForRecording(const IntRect& rect)
+{
+    m_visibleContentRectForRecording.reset(new IntRect(rect));
+}
+
+void FrameView::resetVisibleContentRectForRecording()
+{
+    m_visibleContentRectForRecording.reset();
+}
+
 IntPoint FrameView::minimumScrollPosition() const
 {
     return IntPoint(-scrollOrigin().x(), -scrollOrigin().y());
@@ -3386,6 +3409,7 @@ void FrameView::setScrollOffset(const DoublePoint& offset, ScrollType scrollType
     if (AXObjectCache* cache = m_frame->document()->existingAXObjectCache())
         cache->handleScrollPositionChanged(this);
 
+    frame().host()->chromeClient().mainFrameScrollOffsetChanged();

[Sami, 2016/08/11 10:09:07]

May need to guard this with m_frame->isMainFrame(). (I also wonder if we could
reuse the didChangeScrollOffset callback below?)

[Eric Seckler, 2016/08/11 11:34:45]

You're right, guarding it now. I looked into the didChangeScrollOffset callback,
but that seems to be used to notify the embedder. I'm using the ChromeClient
path, because that's already used for similar things, e.g.
pageScaleFactorChanged() and layoutChanged().

     frame().loader().saveScrollState();
     frame().loader().client()->didChangeScrollOffset();