Only promote fixed position elements on low dpi without transform or opacity.

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/layout/compositing/CompositedLayerMapping.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/api/LayoutViewItem.h"
@@ skipping 773 matching lines @@
   ASSERT_TRUE(frameDocument.view()->layoutViewItem().hasLayer());
   // The width is 485 pixels due to the size of the scrollbar.
   EXPECT_RECT_EQ(
       IntRect(0, 0, 500, 7500),
       recomputeInterestRect(frameDocument.view()
                                 ->layoutViewItem()
                                 .enclosingLayer()
                                 ->graphicsLayerBackingForScrolling()));
 }
 
-TEST_P(CompositedLayerMappingTest, PromoteOpaqueFixedPosition) {
-  const bool preferCompositing =
-      document().frame()->settings()->preferCompositingToLCDTextEnabled();
-  document().frame()->settings()->setPreferCompositingToLCDTextEnabled(false);
-  ScopedCompositeFixedPositionForTest compositeFixedPosition(true);
-
-  setBodyInnerHTML(
-      "<div id='translucent' style='width: 20px; height: 20px; position: "
-      "fixed; top: 100px; left: 100px;'></div>"
-      "<div id='opaque' style='width: 20px; height: 20px; position: fixed; "
-      "top: 100px; left: 200px; background: white;'></div>"
-      "<div id='opaque-with-shadow' style='width: 20px; height: 20px; "
-      "position: fixed; top: 100px; left: 300px; background: white; "
-      "box-shadow: 10px 10px 5px #888888;'></div>"
-      "<div id='spacer' style='height: 2000px'></div>");
-
-  document().view()->updateAllLifecyclePhases();
-
-  // The translucent fixed box should not be promoted.
-  Element* element = document().getElementById("translucent");
-  PaintLayer* paintLayer =
-      toLayoutBoxModelObject(element->layoutObject())->layer();
-  EXPECT_EQ(NotComposited, paintLayer->compositingState());
-
-  // The opaque fixed box should be promoted and be opaque so that text will be
-  // drawn with subpixel anti-aliasing.
-  element = document().getElementById("opaque");
-  paintLayer = toLayoutBoxModelObject(element->layoutObject())->layer();
-  EXPECT_EQ(PaintsIntoOwnBacking, paintLayer->compositingState());
-  EXPECT_TRUE(paintLayer->graphicsLayerBacking()->contentsOpaque());
-
-  // The opaque fixed box with shadow should not be promoted because the layer
-  // will include the shadow which is not opaque.
-  element = document().getElementById("opaque-with-shadow");
-  paintLayer = toLayoutBoxModelObject(element->layoutObject())->layer();
-  EXPECT_EQ(NotComposited, paintLayer->compositingState());
-
-  document().frame()->settings()->setPreferCompositingToLCDTextEnabled(
-      preferCompositing);
-}
-
 TEST_P(CompositedLayerMappingTest,
        ScrollingContentsAndForegroundLayerPaintingPhase) {
   document().frame()->settings()->setPreferCompositingToLCDTextEnabled(true);
   setBodyInnerHTML(
       "<div id='container' style='position: relative; z-index: 1; overflow: "
       "scroll; width: 300px; height: 300px'>"
       "    <div id='negative-composited-child' style='background-color: red; "
       "width: 1px; height: 1px; position: absolute; backface-visibility: "
       "hidden; z-index: -1'></div>"
       "    <div style='background-color: blue; width: 2000px; height: 2000px; "
@@ skipping 197 matching lines @@
     document().view()->updateAllLifecyclePhases();
     ASSERT_EQ(document().documentElement(),
               rootScrollerController.globalRootScroller());
 
     EXPECT_TRUE(mapping3->clippingLayer());
     EXPECT_TRUE(mapping3->clippingLayer()->platformLayer()->masksToBounds());
   }
 }
 
 }  // namespace blink