Adds scroll position/scale emulation to DevTools.

third_party/WebKit/Source/core/frame/VisualViewport.cpp

Index: third_party/WebKit/Source/core/frame/VisualViewport.cpp
diff --git a/third_party/WebKit/Source/core/frame/VisualViewport.cpp b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
index cd084315dbc2d67e73b76e8f9d61c6c8ca7a5581..fa2ea94b95ec47122d48a64e06fe2e7a9afcfdcd 100644
--- a/third_party/WebKit/Source/core/frame/VisualViewport.cpp
+++ b/third_party/WebKit/Source/core/frame/VisualViewport.cpp
@@ -71,6 +71,8 @@ VisualViewport::VisualViewport(FrameHost& owner)
     , m_topControlsAdjustment(0)
     , m_maxPageScale(-1)
     , m_trackPinchZoomStatsForPage(false)
+    , m_scaleAndScrollOverrideEnabled(false)
+    , m_scaleAndScrollOverrideScale(0)
 {
     reset();
 }
@@ -210,6 +212,21 @@ void VisualViewport::setScale(float scale)
     setScaleAndLocation(scale, m_offset);
 }
 
+void VisualViewport::setScaleAndScrollOverride(float scale, const FloatPoint& location)
+{
+    m_scaleAndScrollOverrideEnabled = true;
+    m_scaleAndScrollOverrideScale = scale;
+    m_scaleAndScrollOverrideLocation = location;
+
+    setScaleAndLocation(this->scale(), this->location());
+}
+
+void VisualViewport::clearScaleAndScrollOverride()
+{
+    m_scaleAndScrollOverrideEnabled = false;
+    reset();
+}
+
 double VisualViewport::scrollLeft()
 {
     if (!mainFrame())
@@ -286,15 +303,18 @@ void VisualViewport::setScaleAndLocation(float scale, const FloatPoint& location
 
     bool valuesChanged = false;
 
-    if (scale != m_scale) {
-        m_scale = scale;
+    float newScale = applyScaleOverrideToScale(scale);
+    if (newScale != m_scale || newScale != scale) {
+        m_scale = newScale;
         valuesChanged = true;
         frameHost().chromeClient().pageScaleFactorChanged();
     }
 
-    FloatPoint clampedOffset(clampOffsetToBoundaries(location));
+    FloatPoint overriddenLocation(applyScrollOverrideToLocation(location));
+    FloatPoint clampedOffset(clampOffsetToBoundaries(overriddenLocation));
 
-    if (clampedOffset != m_offset) {
+    // When location was overridden, re-apply override to counteract potential scroll animations by compositor.
+    if (clampedOffset != m_offset || overriddenLocation != location) {
         m_offset = clampedOffset;
         scrollAnimator().setCurrentPosition(m_offset);
 
@@ -691,6 +711,25 @@ void VisualViewport::clampToBoundaries()
     setLocation(m_offset);
 }
 
+FloatPoint VisualViewport::applyScrollOverrideToLocation(const FloatPoint& location)
+{
+    FloatPoint newLocation = location;
+    if (m_scaleAndScrollOverrideEnabled) {
+        if (m_scaleAndScrollOverrideLocation.x() >= 0)

[Sami, 2016/06/23 17:34:03]

Ditto.

+            newLocation.setX(m_scaleAndScrollOverrideLocation.x());
+        if (m_scaleAndScrollOverrideLocation.y() >= 0)
+            newLocation.setY(m_scaleAndScrollOverrideLocation.y());
+    }
+    return newLocation;
+}
+
+float VisualViewport::applyScaleOverrideToScale(float scale)
+{
+    if (m_scaleAndScrollOverrideEnabled && m_scaleAndScrollOverrideScale > 0)
+        return m_scaleAndScrollOverrideScale;
+    return scale;
+}
+
 FloatRect VisualViewport::viewportToRootFrame(const FloatRect& rectInViewport) const
 {
     FloatRect rectInRootFrame = rectInViewport;