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 7f9d5c550cfe56d0f26f919d9bc120bda193ac41..122a2f36b3ddf7b46cb3ad6e2fd35b77b0ef761c 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"
@@ -3207,6 +3208,57 @@ WebFloatSize WebViewImpl::visualViewportSize() const
     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)
@@ -3832,10 +3884,12 @@ 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();
 }