Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 38 matching lines @@
 #include "core/events/KeyboardEvent.h"
 #include "core/events/UIEventWithKeyState.h"
 #include "core/events/WheelEvent.h"
 #include "core/fetch/UniqueIdentifier.h"
 #include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/PageScaleConstraintsSet.h"
 #include "core/frame/RemoteFrame.h"
+#include "core/frame/ScrollAndScaleEmulator.h"
 #include "core/frame/Settings.h"
 #include "core/frame/SmartClip.h"
 #include "core/frame/TopControls.h"
 #include "core/frame/UseCounter.h"
 #include "core/frame/VisualViewport.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/HTMLMediaElement.h"
 #include "core/html/HTMLPlugInElement.h"
 #include "core/html/HTMLTextAreaElement.h"
 #include "core/input/EventHandler.h"
@@ skipping 3131 matching lines @@
     DCHECK(page());
     return page()->frameHost().visualViewport().visibleRect().location();
 }
 
 WebFloatSize WebViewImpl::visualViewportSize() const
 {
     DCHECK(page());
     return page()->frameHost().visualViewport().visibleRect().size();
 }
 
+void WebViewImpl::setScrollAndScaleOverride(const WebDeviceEmulationParams& params)
+{
+    if (!page())
+        return;
+
+    if (!mainFrameImpl())
+        return;
+
+    FrameView * view = mainFrameImpl()->frameView();
+    if (!view)
+        return;
+
+    if (!m_scrollAndScaleEmulator) {
+        m_scrollAndScaleEmulator = ScrollAndScaleEmulator::create();
+    }
+
+    bool hasChanged = m_scrollAndScaleEmulator->update(
+        static_cast<IntPoint>(params.scrollPosition),
+        static_cast<FloatPoint>(params.visualViewportPosition),
+        params.visualViewportScale);
+    if (hasChanged) {
+        view->setScrollAndScaleEmulator(m_scrollAndScaleEmulator);
+        page()->frameHost().visualViewport().setScrollAndScaleEmulator(m_scrollAndScaleEmulator);
+        page()->frameHost().setUserAgentPageScaleConstraints(
+            m_scrollAndScaleEmulator->pageScaleConstraints());
+    }

[bokan, 2016/06/29 15:15:49]

My recommendation for the mainFrameSize issue would be to add a similar pattern
to what you have in the minimum/maximumScrollPosition methods to override the
mainFrameSize. In the cases where the main frame size isn't overridden you can
save the current minimumPageScaleFactor here and just return the frame size
divided by this. Alternatively, you could get what the minimumPageScaleFactor
"should" be by clearing the UA constraints, calculating the final constraints,
then reapplying the UA constraints. A bit uglier but more robust since it'll
apply any changes made by the page (should be pretty rare). Does that sound ok?

+}
+
+void WebViewImpl::clearScrollAndScaleOverride()
+{
+    if (!m_scrollAndScaleEmulator)
+        return;
+
+    if (!page())
+        return;
+
+    if (!mainFrameImpl())
+        return;
+
+    FrameView * view = mainFrameImpl()->frameView();
+    if (!view)
+        return;
+
+    m_scrollAndScaleEmulator.clear();
+    view->setScrollAndScaleEmulator(m_scrollAndScaleEmulator);
+    page()->frameHost().visualViewport().setScrollAndScaleEmulator(m_scrollAndScaleEmulator);
+    page()->frameHost().setUserAgentPageScaleConstraints(PageScaleConstraints());
+
+    resetScrollAndScaleState();
+}
+
 void WebViewImpl::scrollAndRescaleViewports(float scaleFactor,
     const IntPoint& mainFrameOrigin,
     const FloatPoint& visualViewportOrigin)
 {
     if (!page())
         return;
 
     if (!mainFrameImpl())
         return;
 
@@ skipping 605 matching lines @@
     m_rootLayerScale = rootLayerScale;
     m_rootLayerOffset = rootLayerOffset;
     if (mainFrameImpl())
         mainFrameImpl()->setInputEventsTransformForEmulation(m_rootLayerOffset, m_rootLayerScale);
     updateRootLayerTransform();
 }
 
 void WebViewImpl::enableDeviceEmulation(const WebDeviceEmulationParams& params)
 {
     m_devToolsEmulator->enableDeviceEmulation(params);
+    setScrollAndScaleOverride(params);
 }
 
 void WebViewImpl::disableDeviceEmulation()
 {
+    clearScrollAndScaleOverride();
     m_devToolsEmulator->disableDeviceEmulation();
 }
 
 WebAXObject WebViewImpl::accessibilityObject()
 {
     if (!mainFrameImpl())
         return WebAXObject();
 
     Document* document = mainFrameImpl()->frame()->document();
     return WebAXObject(toAXObjectCacheImpl(document->axObjectCache())->root());
@@ skipping 672 matching lines @@
 {
     // TODO(oshima): Investigate if this should return the ScreenInfo's scale factor rather than
     // page's scale factor, which can be 1 in use-zoom-for-dsf mode.
     if (!page())
         return 1;
 
     return page()->deviceScaleFactor();
 }
 
 } // namespace blink