Skip overflow adjustment checks when possible in StyleAdjuster

Continuing the work to make StyleAdjuster cheaper we can skip all the work
related to overflow adjustment in the common case when overflow is visible.

Review URL: https://codereview.chromium.org/214413011

git-svn-id: svn://svn.chromium.org/blink/trunk@170306 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.cpp

@@ -231,8 +231,7 @@ void StyleAdjuster::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
         || style->position() == StickyPosition
         || style->position() == FixedPosition
         || isInTopLayer(e, style)
-        || hasWillChangeThatCreatesStackingContext(style, e)
-        ))
+        || hasWillChangeThatCreatesStackingContext(style, e)))
         style->setZIndex(0);
 
     // will-change:transform should result in the same rendering behavior as having a transform,
@@ -247,31 +246,8 @@ void StyleAdjuster::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
     else
         style->addToTextDecorationsInEffect(style->textDecoration());
 
-    // If either overflow value is not visible, change to auto.
-    if (style->overflowX() == OVISIBLE && style->overflowY() != OVISIBLE) {
-        // FIXME: Once we implement pagination controls, overflow-x should default to hidden
-        // if overflow-y is set to -webkit-paged-x or -webkit-page-y. For now, we'll let it
-        // default to auto so we can at least scroll through the pages.
-        style->setOverflowX(OAUTO);
-    } else if (style->overflowY() == OVISIBLE && style->overflowX() != OVISIBLE) {
-        style->setOverflowY(OAUTO);
-    }
-
-    // Table rows, sections and the table itself will support overflow:hidden and will ignore scroll/auto.
-    // FIXME: Eventually table sections will support auto and scroll.
-    if (style->display() == TABLE || style->display() == INLINE_TABLE
-        || style->display() == TABLE_ROW_GROUP || style->display() == TABLE_ROW) {
-        if (style->overflowX() != OVISIBLE && style->overflowX() != OHIDDEN)
-            style->setOverflowX(OVISIBLE);
-        if (style->overflowY() != OVISIBLE && style->overflowY() != OHIDDEN)
-            style->setOverflowY(OVISIBLE);
-    }
-
-    // Menulists should have visible overflow
-    if (style->appearance() == MenulistPart) {
-        style->setOverflowX(OVISIBLE);
-        style->setOverflowY(OVISIBLE);
-    }
+    if (style->overflowX() != OVISIBLE || style->overflowY() != OVISIBLE)
+        adjustOverflow(style, e);
 
     // Cull out any useless layers and also repeat patterns into additional layers.
     style->adjustBackgroundLayers();
@@ -292,17 +268,6 @@ void StyleAdjuster::adjustRenderStyle(RenderStyle* style, RenderStyle* parentSty
         style->setTransformStyle3D(TransformStyle3DFlat);
 
     if (e && e->isSVGElement()) {
-        // Spec: http://www.w3.org/TR/SVG/masking.html#OverflowProperty
-        if (style->overflowY() == OSCROLL)
-            style->setOverflowY(OHIDDEN);
-        else if (style->overflowY() == OAUTO)
-            style->setOverflowY(OVISIBLE);
-
-        if (style->overflowX() == OSCROLL)
-            style->setOverflowX(OHIDDEN);
-        else if (style->overflowX() == OAUTO)
-            style->setOverflowX(OVISIBLE);
-
         // Only the root <svg> element in an SVG document fragment tree honors css position
         if (!(isSVGSVGElement(*e) && e->parentNode() && !e->parentNode()->isSVGElement()))
             style->setPosition(RenderStyle::initialPosition());
@@ -403,6 +368,50 @@ void StyleAdjuster::adjustStyleForTagName(RenderStyle* style, RenderStyle* paren
     }
 }
 
+void StyleAdjuster::adjustOverflow(RenderStyle* style, Element* element)
+{
+    ASSERT(style->overflowX() != OVISIBLE || style->overflowY() != OVISIBLE);
+
+    // If either overflow value is not visible, change to auto.
+    if (style->overflowX() == OVISIBLE && style->overflowY() != OVISIBLE) {
+        // FIXME: Once we implement pagination controls, overflow-x should default to hidden
+        // if overflow-y is set to -webkit-paged-x or -webkit-page-y. For now, we'll let it
+        // default to auto so we can at least scroll through the pages.
+        style->setOverflowX(OAUTO);
+    } else if (style->overflowY() == OVISIBLE && style->overflowX() != OVISIBLE) {
+        style->setOverflowY(OAUTO);
+    }
+
+    // Table rows, sections and the table itself will support overflow:hidden and will ignore scroll/auto.
+    // FIXME: Eventually table sections will support auto and scroll.
+    if (style->display() == TABLE || style->display() == INLINE_TABLE
+        || style->display() == TABLE_ROW_GROUP || style->display() == TABLE_ROW) {
+        if (style->overflowX() != OVISIBLE && style->overflowX() != OHIDDEN)
+            style->setOverflowX(OVISIBLE);
+        if (style->overflowY() != OVISIBLE && style->overflowY() != OHIDDEN)
+            style->setOverflowY(OVISIBLE);
+    }
+
+    // Menulists should have visible overflow
+    if (style->appearance() == MenulistPart) {
+        style->setOverflowX(OVISIBLE);
+        style->setOverflowY(OVISIBLE);
+    }
+
+    // Spec: http://www.w3.org/TR/SVG/masking.html#OverflowProperty
+    if (element && element->isSVGElement()) {
+        if (style->overflowY() == OSCROLL)
+            style->setOverflowY(OHIDDEN);
+        else if (style->overflowY() == OAUTO)
+            style->setOverflowY(OVISIBLE);
+
+        if (style->overflowX() == OSCROLL)
+            style->setOverflowX(OHIDDEN);
+        else if (style->overflowX() == OAUTO)
+            style->setOverflowX(OVISIBLE);
+    }
+}
+
 void StyleAdjuster::adjustStyleForDisplay(RenderStyle* style, RenderStyle* parentStyle)
 {
     if (style->display() == BLOCK && !style->isFloating())

third_party/WebKit/Source/core/css/resolver/StyleAdjuster.h

@@ -43,6 +43,7 @@ public:
 private:
     void adjustStyleForDisplay(RenderStyle* styleToAdjust, RenderStyle* parentStyle);
     void adjustStyleForTagName(RenderStyle* styleToAdjust, RenderStyle* parentStyle, Element&);
+    void adjustOverflow(RenderStyle* styleToAdjust, Element*);
 
     const CachedUAStyle& m_cachedUAStyle;
     bool m_useQuirksModeStyles;