Base new scale on minimum-scale after orientation change.

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 1622 matching lines @@
 
 void WebViewImpl::resize(const WebSize& newSize)
 {
     if (m_shouldAutoResize || m_size == newSize)
         return;
 
     FrameView* view = localFrameRootTemporary()->frameView();
     if (!view)
         return;
 
-    WebSize oldSize = m_size;
+    bool shouldAnchorAndRescaleViewport = settings()->mainFrameResizesAreOrientationChanges()
+        && m_size.width && contentsSize().width() && newSize.width != m_size.width && !m_fullscreenController->isFullscreen();
     float oldPageScaleFactor = pageScaleFactor();
-    int oldContentsWidth = contentsSize().width();
+    float oldMinimumPageScaleFactor = minimumPageScaleFactor();
 
     m_size = newSize;
 
-    bool shouldAnchorAndRescaleViewport = settings()->mainFrameResizesAreOrientationChanges()
-        && oldSize.width && oldContentsWidth && newSize.width != oldSize.width && !m_fullscreenController->isFullscreen();
-
     ViewportAnchor viewportAnchor(&localFrameRootTemporary()->frame()->eventHandler());
     if (shouldAnchorAndRescaleViewport) {
         viewportAnchor.setAnchor(view->visibleContentRect(),
                                  FloatSize(viewportAnchorXCoord, viewportAnchorYCoord));
     }
 
     // FIXME: FastTextAutosizer does not yet support out-of-process frames.
     if (mainFrameImpl() && mainFrameImpl()->frame()->isLocalFrame())
     {
         // Avoids unnecessary invalidations while various bits of state in FastTextAutosizer are updated.
         FastTextAutosizer::DeferUpdatePageInfo deferUpdatePageInfo(page());
         performResize();
     } else {
         performResize();
     }
 
     if (settings()->viewportEnabled() && !m_fixedLayoutSizeLock) {
         // Relayout immediately to recalculate the minimum scale limit.
         if (view->needsLayout())
             view->layout();
 
         if (shouldAnchorAndRescaleViewport) {
-            float viewportWidthRatio = static_cast<float>(newSize.width) / oldSize.width;
-            float contentsWidthRatio = static_cast<float>(contentsSize().width()) / oldContentsWidth;
-            float scaleMultiplier = viewportWidthRatio / contentsWidthRatio;
-
-            IntSize viewportSize = view->visibleContentRect().size();
-            if (scaleMultiplier != 1) {
-                float newPageScaleFactor = oldPageScaleFactor * scaleMultiplier;
-                viewportSize.scale(pageScaleFactor() / newPageScaleFactor);
-                IntPoint scrollOffsetAtNewScale = viewportAnchor.computeOrigin(viewportSize);
-                setPageScaleFactor(newPageScaleFactor, scrollOffsetAtNewScale);
-            } else {
-                IntPoint scrollOffsetAtNewScale = clampOffsetAtScale(viewportAnchor.computeOrigin(viewportSize), pageScaleFactor());
-                updateMainFrameScrollPosition(scrollOffsetAtNewScale, false);
-            }
+            float newPageScaleFactor = oldPageScaleFactor / oldMinimumPageScaleFactor * minimumPageScaleFactor();
+            IntSize scaledViewportSize = newSize;
+            scaledViewportSize.scale(1 / newPageScaleFactor);
+            setPageScaleFactor(newPageScaleFactor, viewportAnchor.computeOrigin(scaledViewportSize));
         }
     }
 
     sendResizeEventAndRepaint();
 }
 
 void WebViewImpl::willEndLiveResize()
 {
     if (mainFrameImpl() && mainFrameImpl()->frameView())
         mainFrameImpl()->frameView()->willEndLiveResize();
@@ skipping 2553 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink