Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/web/DevToolsEmulator.h

Index: third_party/WebKit/Source/web/DevToolsEmulator.h
diff --git a/third_party/WebKit/Source/web/DevToolsEmulator.h b/third_party/WebKit/Source/web/DevToolsEmulator.h
index 07836526e34fbc6b10560e8bfe291d7ce2486c8d..f8a9d3ea21f7264ea6edf02fce8ec06a1038f7a6 100644
--- a/third_party/WebKit/Source/web/DevToolsEmulator.h
+++ b/third_party/WebKit/Source/web/DevToolsEmulator.h
@@ -7,15 +7,19 @@
 
 #include "platform/heap/Handle.h"
 #include "public/platform/PointerProperties.h"
+#include "public/platform/WebFloatRect.h"
 #include "public/platform/WebViewportStyle.h"
 #include "public/web/WebDeviceEmulationParams.h"
 #include "wtf/Forward.h"
+#include "wtf/Optional.h"
 #include <memory>
 
 namespace blink {
 
 class InspectorEmulationAgent;
 class IntPoint;
+class TransformationMatrix;
+struct WebFloatRect;
 class WebInputEvent;
 class WebViewImpl;
 
@@ -44,23 +48,40 @@ public:
     // Emulation.
     void enableDeviceEmulation(const WebDeviceEmulationParams&);
     void disableDeviceEmulation();
+    void setVisualTransformOverride(const WebFloatRect& area, float scale);
+    void clearVisualTransformOverride();
     bool resizeIsDeviceSizeChange();
     void setTouchEventEmulationEnabled(bool);
     bool handleInputEvent(const WebInputEvent&);
     void setScriptExecutionDisabled(bool);
 
+    // Notify the DevToolsEmulator about a scroll or scale change of the main
+    // frame. Updates the transform for an visual transform override.
+    void mainFrameScrollOrScaleChanged();
+
 private:
     explicit DevToolsEmulator(WebViewImpl*);
 
     void enableMobileEmulation();
     void disableMobileEmulation();
 
+    void applyDeviceEmulationTransform(TransformationMatrix*);
+    void applyVisualTransformOverride(TransformationMatrix*);
+    void updateRootLayerTransform();
+
     WebViewImpl* m_webViewImpl;
 
     bool m_deviceMetricsEnabled;
     bool m_emulateMobileEnabled;
     WebDeviceEmulationParams m_emulationParams;
 
+    struct VisualTransformOverride {
+        WebFloatRect area;
+        double scale;
+        bool originalVisualViewportMasking;
+    };
+    WTF::Optional<VisualTransformOverride> m_visualTransformOverride;
+
     bool m_isOverlayScrollbarsEnabled;
     bool m_isOrientationEventEnabled;
     bool m_isMobileLayoutThemeEnabled;