Widen GPU trigger condition

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 3233 matching lines @@
         view->layout();
 }
 
 void WebViewImpl::updatePageDefinedViewportConstraints(const ViewportDescription& description)
 {
     if (!settings()->viewportEnabled() || !page() || (!m_size.width && !m_size.height) || !page()->mainFrame()->isLocalFrame())
         return;
 
     Document* document = page()->deprecatedLocalMainFrame()->document();
 
-    m_matchesHeuristicsForGpuRasterization = description.maxWidth == Length(DeviceWidth)
-        && description.minZoom == 1.0
-        && description.minZoomIsExplicit;
-    if (m_layerTreeView)
-        m_layerTreeView->heuristicsForGpuRasterizationUpdated(m_matchesHeuristicsForGpuRasterization);
-
     Length defaultMinWidth = document->viewportDefaultMinWidth();
     if (defaultMinWidth.isAuto())
         defaultMinWidth = Length(ExtendToZoom);
 
     ViewportDescription adjustedDescription = description;
     if (settingsImpl()->viewportMetaLayoutSizeQuirk() && adjustedDescription.type == ViewportDescription::ViewportMeta) {
         const int legacyWidthSnappingMagicNumber = 320;
         if (adjustedDescription.maxWidth.isFixed() && adjustedDescription.maxWidth.value() <= legacyWidthSnappingMagicNumber)
             adjustedDescription.maxWidth = Length(DeviceWidth);
         if (adjustedDescription.maxHeight.isFixed() && adjustedDescription.maxHeight.value() <= m_size.height)
             adjustedDescription.maxHeight = Length(DeviceHeight);
         adjustedDescription.minWidth = adjustedDescription.maxWidth;
         adjustedDescription.minHeight = adjustedDescription.maxHeight;
     }
 
     float oldInitialScale = m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale;
     m_pageScaleConstraintsSet.updatePageDefinedConstraints(adjustedDescription, defaultMinWidth);
 
     if (settingsImpl()->clobberUserAgentInitialScaleQuirk()
         && m_pageScaleConstraintsSet.userAgentConstraints().initialScale != -1
         && m_pageScaleConstraintsSet.userAgentConstraints().initialScale * deviceScaleFactor() <= 1) {
         if (description.maxWidth == Length(DeviceWidth)
             || (description.maxWidth.type() == Auto && m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale == 1.0f))
             setInitialPageScaleOverride(-1);
     }
 
+    m_matchesHeuristicsForGpuRasterization = description.maxWidth == Length(DeviceWidth)
+        && (m_pageScaleConstraintsSet.pageDefinedConstraints().minimumScale >= 1.0
+            || (!description.userZoom && m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale >= 1.0));
+    if (m_layerTreeView)
+        m_layerTreeView->heuristicsForGpuRasterizationUpdated(m_matchesHeuristicsForGpuRasterization);
+

[ajuma, 2014/10/21 17:40:03]

I understand the motivation of using the resolved values, but I think it makes
things harder to explain to web developers. I'd prefer to do something similar
using |description| directly (as before). For example, how about:
 m_matchesHeuristicsForGpuRasterization = description.maxWidth ==
Length(DeviceWidth)	
         && ((description.minZoom >= 1.0 && description.minZoomIsExplicit)
             || (description.userZoom == false && description.zoom >= 1.0 &&
description.zoomIsExplicit));

This allows viewports that meet either of the following conditions:
1) width=device-width, minimum-scale=X, where X >= 1.0
2) width=device-width, user-scalable=no, initial-scale=X, where X >= 1.0

     m_pageScaleConstraintsSet.adjustForAndroidWebViewQuirks(adjustedDescription, defaultMinWidth.intValue(), deviceScaleFactor(), settingsImpl()->supportDeprecatedTargetDensityDPI(), page()->settings().wideViewportQuirkEnabled(), page()->settings().useWideViewport(), page()->settings().loadWithOverviewMode(), settingsImpl()->viewportMetaNonUserScalableQuirk());
     float newInitialScale = m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale;
     if (oldInitialScale != newInitialScale && newInitialScale != -1) {
         m_pageScaleConstraintsSet.setNeedsReset(true);
         if (mainFrameImpl() && mainFrameImpl()->frameView())
             mainFrameImpl()->frameView()->setNeedsLayout();
     }
 
     updateMainFrameLayoutSize();
 
@@ skipping 1170 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