Merge r230480 - Do not layout images when we only need the overflow i…

…nformation.

https://bugs.webkit.org/show_bug.cgi?id=175331

Reviewed by Simon Fraser.

This improves MotionMark's Simple Leaves by ~10%.

Covered by existing tests.

* rendering/RenderImage.cpp:
(WebCore::RenderImage::layout):

Source/WebCore/ChangeLog

@@ -1,3 +1,17 @@
+2018-04-10  Zalan Bujtas  <zalan@apple.com>
+
+        Do not layout images when we only need the overflow information.
+        https://bugs.webkit.org/show_bug.cgi?id=175331
+
+        Reviewed by Simon Fraser.
+
+        This improves MotionMark's Simple Leaves by ~10%. 
+
+        Covered by existing tests.
+
+        * rendering/RenderImage.cpp:
+        (WebCore::RenderImage::layout):
+
 2018-04-09  Michael Catanzaro  <mcatanzaro@igalia.com>
 
         Unreviewed, rolling out r230390.

Source/WebCore/rendering/RenderImage.cpp

@@ -699,6 +699,12 @@ bool RenderImage::canHaveChildren() const
 
 void RenderImage::layout()
 {
+    // Recomputing overflow is required only when child content is present. 
+    if (needsSimplifiedNormalFlowLayout() && !m_hasShadowControls) {
+        clearNeedsLayout();
+        return;
+    }
+
     StackStats::LayoutCheckPoint layoutCheckPoint;
 
     LayoutSize oldSize = contentBoxRect().size();