Use control clip rather than overflow clip when present for PaintLayers.

third_party/WebKit/Source/core/paint/PaintLayerClipperTest.cpp

 // Copyright 2016 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/paint/PaintLayerClipper.h"
 
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
 #include "core/paint/PaintLayer.h"
@@ skipping 83 matching lines @@
 #else
   // If the PaintLayer clips overflow, the background rect is intersected with
   // the PaintLayer bounds...
   EXPECT_EQ(LayoutRect(8, 8, 200, 300), backgroundRect.rect());
   // and the foreground rect is intersected with the control clip in this case.
   EXPECT_EQ(LayoutRect(10, 10, 196, 296), foregroundRect.rect());
   EXPECT_EQ(LayoutRect(8, 8, 200, 300), layerBounds);
 #endif
 }
 
+TEST_P(PaintLayerClipperTest, ControlClipSelect) {
+  setBodyInnerHTML(
+      "<select id='target' style='position: relative; width: 100px; "
+      "    background: none; border: none; padding: 0px 15px 0px 5px;'>"
+      "  <option>"
+      "    Test long texttttttttttttttttttttttttttttttt"
+      "  </option>"
+      "</select>");
+  Element* target = document().getElementById("target");
+  PaintLayer* targetPaintLayer =
+      toLayoutBoxModelObject(target->layoutObject())->layer();
+  ClipRectsContext context(document().layoutView()->layer(), UncachedClipRects);
+  // When RLS is enabled, the LayoutView will have a composited scrolling layer,
+  // so don't apply an overflow clip.
+  if (RuntimeEnabledFeatures::rootLayerScrollingEnabled())
+    context.setIgnoreOverflowClip();
+  LayoutRect layerBounds;
+  ClipRect backgroundRect, foregroundRect;
+  targetPaintLayer->clipper().calculateRects(
+      context, LayoutRect(LayoutRect::infiniteIntRect()), layerBounds,
+      backgroundRect, foregroundRect);
+// The control clip for a select excludes the area for the down arrow.
+#if OS(MACOSX)
+  EXPECT_EQ(LayoutRect(16, 9, 79, 13), foregroundRect.rect());
+#elif OS(WIN)
+  EXPECT_EQ(LayoutRect(17, 9, 60, 16), foregroundRect.rect());
+#else
+  EXPECT_EQ(LayoutRect(17, 9, 60, 15), foregroundRect.rect());
+#endif
+}
+
 TEST_P(PaintLayerClipperTest, LayoutSVGRootChild) {
   setBodyInnerHTML(
       "<svg width=200 height=300 style='position: relative'>"
       "  <foreignObject width=400 height=500>"
       "    <div id=target xmlns='http://www.w3.org/1999/xhtml' "
       "style='position: relative'></div>"
       "  </foreignObject>"
       "</svg>");
 
   Element* target = document().getElementById("target");
@@ skipping 188 matching lines @@
 
   parent->clipper().clearClipRectsIncludingDescendants(AbsoluteClipRects);
 
   EXPECT_TRUE(parent->clipRectsCache());
   EXPECT_TRUE(child->clipRectsCache());
   EXPECT_FALSE(parent->clipRectsCache()->get(AbsoluteClipRects).root);
   EXPECT_FALSE(parent->clipRectsCache()->get(AbsoluteClipRects).root);
 }
 
 }  // namespace blink