Adds DevTools commands for forced viewport override.

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

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 173 matching lines @@
     void adjustViewSizeAndLayout();
 
     // Scale used to convert incoming input events.
     float inputEventsScaleFactor() const;
 
     // Offset used to convert incoming input events while emulating device metics.
     IntSize inputEventsOffsetForEmulation() const;
     void setInputEventsTransformForEmulation(const IntSize&, float);
 
     void setScrollPosition(const DoublePoint&, ScrollType, ScrollBehavior = ScrollBehaviorInstant) override;
+    void didChangeScrollOffset();
 
     void didUpdateElasticOverscroll();
 
     void viewportSizeChanged(bool widthChanged, bool heightChanged);
 
     AtomicString mediaType() const;
     void setMediaType(const AtomicString&);
     void adjustMediaTypeForPrinting(bool printing);
 
     WebDisplayMode displayMode() { return m_displayMode; }
@@ skipping 239 matching lines @@
 
     bool canHaveScrollbars() const { return horizontalScrollbarMode() != ScrollbarAlwaysOff || verticalScrollbarMode() != ScrollbarAlwaysOff; }
 
     // The visible content rect has a location that is the scrolled offset of
     // the document. The width and height are the layout viewport width and
     // height. By default the scrollbars themselves are excluded from this
     // rectangle, but an optional boolean argument allows them to be included.
     IntRect visibleContentRect(IncludeScrollbarsInRect = ExcludeScrollbars) const override;
     IntSize visibleContentSize(IncludeScrollbarsInRect = ExcludeScrollbars) const;
 
+    // Clips the provided rect to the visible content area. For this purpose, we
+    // also query the chrome client for any active overrides to the visible area
+    // (e.g. DevTool's viewport override).
+    void clipPaintRect(FloatRect*) const;

[chrishtr, 2016/08/22 22:00:42]

Why provide a clipPaintRect method instead of just returning the rect to clip
by?

[Eric Seckler, 2016/08/23 09:32:18]

Actually, because I was thinking we could move the mainFrameClipsContent() check
from CompositedLayerMapping there (and simply not clip if it is false) for the
time being. See also the comment below about eventually unifying
record_whole_document with clipping to the device viewport.

On 2016/08/22 22:22:06, dgozman wrote:
I agree, that would be optimal - provided that we are correct in the assumption
that Android WebView sets the device viewport size to the size of the canvas
provided to WebView.onDraw(). In any case, I think changing the behavior of
record_whole_document will require some further discussion with Android WebView
folks, since it may require changes in public WebView API
(record_whole_document/enableSlowWholeDocumentDraw() should probably be renamed
/ comments updated). If possible, I'd prefer not to make this patch dependent on
the outcome of that discussion, so would suggest to tackle this as a follow-up.
Does that sound reasonable?

+
     // Functions for getting/setting the size of the document contained inside the FrameView (as an IntSize or as individual width and height
     // values).
     IntSize contentsSize() const override; // Always at least as big as the visibleWidth()/visibleHeight().
     int contentsWidth() const { return contentsSize().width(); }
     int contentsHeight() const { return contentsSize().height(); }
 
     // Functions for querying the current scrolled position (both as a point, a size, or as individual X and Y values).
     // Be careful in using the Double version scrollPositionDouble() and scrollOffsetDouble(). They are meant to be
     // used to communicate the fractional scroll position/offset with chromium compositor which can do sub-pixel positioning.
     // Do not call these if the scroll position/offset is used in Blink for positioning. Use the Int version instead.
@@ skipping 408 matching lines @@
     ScrollbarMode m_verticalScrollbarMode;
 
     bool m_horizontalScrollbarLock;
     bool m_verticalScrollbarLock;
 
     ChildrenWidgetSet m_children;
 
     DoubleSize m_pendingScrollDelta;
     DoublePoint m_scrollPosition;
     IntSize m_contentsSize;
+    WTF::Optional<IntRect> m_visibleContentRectForPainting;
 
     int m_scrollbarsAvoidingResizer;
     bool m_scrollbarsSuppressed;
 
     bool m_inUpdateScrollbars;
 
     std::unique_ptr<LayoutAnalyzer> m_analyzer;
 
     // Mark if something has changed in the mapping from Frame to GraphicsLayer
     // and the Frame Timing regions should be recalculated.
@@ skipping 72 matching lines @@
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView, ScrollableArea, scrollableArea, scrollableArea->isFrameView(), scrollableArea.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h