Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/web/WebViewImpl.cpp

Index: third_party/WebKit/Source/web/WebViewImpl.cpp
diff --git a/third_party/WebKit/Source/web/WebViewImpl.cpp b/third_party/WebKit/Source/web/WebViewImpl.cpp
index 3e92e32a2f867341300bb60c550f5729a13a1c55..22bb37d2f703d040b1712d3261b0758e80120ef5 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.cpp
+++ b/third_party/WebKit/Source/web/WebViewImpl.cpp
@@ -56,6 +56,7 @@
 #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"
@@ -3208,6 +3209,31 @@ WebFloatSize WebViewImpl::visualViewportSize() const
     return page()->frameHost().visualViewport().visibleRect().size();
 }
 
+void WebViewImpl::setScrollAndScaleOverride(const WebDeviceEmulationParams& params)
+{
+    if (!page())
+        return;
+
+    if (!m_scrollAndScaleEmulator) {
+        m_scrollAndScaleEmulator = ScrollAndScaleEmulator::create(page());
+    }
+
+    m_scrollAndScaleEmulator->update(
+        page(), static_cast<IntPoint>(params.scrollPosition),
+        static_cast<FloatPoint>(params.visualViewportPosition),
+        params.visualViewportScale);
+}
+
+void WebViewImpl::clearScrollAndScaleOverride()
+{
+    if (!m_scrollAndScaleEmulator || !page())
+        return;
+
+    m_scrollAndScaleEmulator->clear(page());
+    m_scrollAndScaleEmulator.clear();
+    resetScrollAndScaleState();
+}
+
 void WebViewImpl::scrollAndRescaleViewports(float scaleFactor,
     const IntPoint& mainFrameOrigin,
     const FloatPoint& visualViewportOrigin)
@@ -3343,7 +3369,13 @@ void WebViewImpl::setIgnoreViewportTagScaleLimits(bool ignore)
 IntSize WebViewImpl::mainFrameSize()
 {
     // The frame size should match the viewport size at minimum scale, since the
-    // viewport must always be contained by the frame.
+    // viewport must always be contained by the frame. As ScrollAndScaleEmulator
+    // may override the minimum scale, it is responsible for this calculation if
+    // it is active.
+    if (m_scrollAndScaleEmulator) {
+        return m_scrollAndScaleEmulator->mainFrameSize(page(), m_size);
+    }
+
     FloatSize frameSize(m_size);
     frameSize.scale(1 / minimumPageScaleFactor());
     return expandedIntSize(frameSize);
@@ -3834,10 +3866,12 @@ void WebViewImpl::setRootLayerTransform(const WebSize& rootLayerOffset, float ro
 void WebViewImpl::enableDeviceEmulation(const WebDeviceEmulationParams& params)
 {
     m_devToolsEmulator->enableDeviceEmulation(params);
+    setScrollAndScaleOverride(params);
 }
 
 void WebViewImpl::disableDeviceEmulation()
 {
+    clearScrollAndScaleOverride();
     m_devToolsEmulator->disableDeviceEmulation();
 }