Separate repaint and layout requirements of StyleDifference (Step 4)

Source/core/rendering/style/RenderStyle.cpp

Index: Source/core/rendering/style/RenderStyle.cpp
diff --git a/Source/core/rendering/style/RenderStyle.cpp b/Source/core/rendering/style/RenderStyle.cpp
index dfeb3bed61f5b2ce8ec111e0e8193140b5c768cd..2256f16c678904a309d2c7082d38b7aeba2504d3 100644
--- a/Source/core/rendering/style/RenderStyle.cpp
+++ b/Source/core/rendering/style/RenderStyle.cpp
@@ -376,6 +376,11 @@ StyleDifference RenderStyle::visualInvalidationDiff(const RenderStyle& other, un
     if (m_svgStyle.get() != other.m_svgStyle.get())
         diff = m_svgStyle->diff(other.m_svgStyle.get());
 
+    if ((!diff.needsFullLayout() || !diff.needsRepaint()) && diffNeedsFullLayoutAndRepaint(other)) {
+        diff.setNeedsFullLayout();
+        diff.setNeedsRepaintObject();
+    }
+
     if (!diff.needsFullLayout() && diffNeedsFullLayout(other))
         diff.setNeedsFullLayout();
 
@@ -411,8 +416,13 @@ StyleDifference RenderStyle::visualInvalidationDiff(const RenderStyle& other, un
     return diff;
 }
 
-bool RenderStyle::diffNeedsFullLayout(const RenderStyle& other) const
+bool RenderStyle::diffNeedsFullLayoutAndRepaint(const RenderStyle& other) const
 {
+    // FIXME: Not all cases in this method need both full layout and repaint.
+    // Should move cases into diffNeedsFullLayout() if
+    // - don't need repaint at all;
+    // - or the renderer knows how to repaint caused by layout change.

[Julien - ping for review, 2014/05/12 15:08:46]

I don't understand this sentence: when do we *not* know how to repaint after a
layout change?

[Xianzhu, 2014/05/12 21:31:51]

I mean the renderer knows how to repaint optimally other than the forced full
repaint. Updated the comments.

+
     if (m_box.get() != other.m_box.get()) {
         if (m_box->width() != other.m_box->width()
             || m_box->minWidth() != other.m_box->minWidth()
@@ -603,6 +613,11 @@ bool RenderStyle::diffNeedsFullLayout(const RenderStyle& other) const
     return false;
 }
 
+bool RenderStyle::diffNeedsFullLayout(const RenderStyle& other) const
+{
+    return false;
+}
+
 bool RenderStyle::diffNeedsRepaintLayer(const RenderStyle& other) const
 {
     if (position() != StaticPosition && (visual->clip != other.visual->clip || visual->hasClip != other.visual->hasClip))