[css-grid] Fix performance regression in grid layout

third_party/WebKit/Source/core/style/GridTrackSize.h

Index: third_party/WebKit/Source/core/style/GridTrackSize.h
diff --git a/third_party/WebKit/Source/core/style/GridTrackSize.h b/third_party/WebKit/Source/core/style/GridTrackSize.h
index 5005aed0e7a8d64b1898cb762a054263930537af..646a7bca949206253b919c16c0526794fa0bd0a6 100644
--- a/third_party/WebKit/Source/core/style/GridTrackSize.h
+++ b/third_party/WebKit/Source/core/style/GridTrackSize.h
@@ -54,9 +54,11 @@ public:
     GridTrackSize(const GridLength& length, GridTrackSizeType trackSizeType = LengthTrackSizing)
         : m_type(trackSizeType)
         , m_minTrackBreadth(trackSizeType == FitContentTrackSizing ? Length(Auto) : length)
-        , m_maxTrackBreadth(length)
+        , m_maxTrackBreadth(trackSizeType == FitContentTrackSizing ? Length(Auto) : length)
+        , m_fitContentTrackBreadth(trackSizeType == FitContentTrackSizing ? length : GridLength(Length(Fixed)))

[Manuel Rego, 2016/09/07 10:56:47]

Probably using Length(Auto) or Length(Fixed) is enough,
like we do for m_min|maxTrackBreadth.

[svillar, 2016/09/07 16:27:52]

Yes, but there is a recent trend to remove the usage of implicit constructors,
that's why I chose that syntax.

     {
         DCHECK(trackSizeType == LengthTrackSizing || trackSizeType == FitContentTrackSizing);
+        DCHECK(trackSizeType != FitContentTrackSizing || length.isLength());
         cacheMinMaxTrackBreadthTypes();
     }
 
@@ -64,19 +66,19 @@ public:
         : m_type(MinMaxTrackSizing)
         , m_minTrackBreadth(minTrackBreadth)
         , m_maxTrackBreadth(maxTrackBreadth)
+        , m_fitContentTrackBreadth(GridLength(Length(Fixed)))
     {
         cacheMinMaxTrackBreadthTypes();
     }
 
-    GridLength length() const
+    const GridLength& fitContentTrackBreadth() const
     {
-        DCHECK(m_type == LengthTrackSizing || m_type == FitContentTrackSizing);
-        DCHECK(m_minTrackBreadth == m_maxTrackBreadth || m_type == FitContentTrackSizing);
-        return m_maxTrackBreadth;
+        DCHECK(m_type == FitContentTrackSizing);
+        return m_fitContentTrackBreadth;
     }
 
-    GridLength minTrackBreadth() const { return m_minTrackBreadth; }
-    GridLength maxTrackBreadth() const { return isFitContent() ? GridLength(Length(MaxContent)) : m_maxTrackBreadth; }
+    const GridLength& minTrackBreadth() const { return m_minTrackBreadth; }
+    const GridLength& maxTrackBreadth() const { return m_maxTrackBreadth; }

[Manuel Rego, 2016/09/07 10:56:47]

Probably you can add here a similar DCHECK() to the one in
fitContentTrackBreadth().

[svillar, 2016/09/07 16:27:52]

To check what? All the different types have a min and a max so there is no much
to check here.

[Manuel Rego, 2016/09/07 20:11:47]

Yes, right didn't realize about that.

I was thinking in doing "DCHECK(m_type != FitContentTrackSizing);"
but I didn't remember that these values were used anyway.

 
     GridTrackSizeType type() const { return m_type; }
 
@@ -115,12 +117,14 @@ private:
     GridTrackSizeType m_type;
     GridLength m_minTrackBreadth;
     GridLength m_maxTrackBreadth;
-    bool m_minTrackBreadthIsAuto;
-    bool m_minTrackBreadthIsMaxContent;
-    bool m_minTrackBreadthIsMinContent;
-    bool m_maxTrackBreadthIsAuto;
-    bool m_maxTrackBreadthIsMaxContent;
-    bool m_maxTrackBreadthIsMinContent;
+    GridLength m_fitContentTrackBreadth;
+
+    bool m_minTrackBreadthIsAuto : 1;
+    bool m_maxTrackBreadthIsAuto : 1;
+    bool m_minTrackBreadthIsMaxContent : 1;
+    bool m_minTrackBreadthIsMinContent : 1;
+    bool m_maxTrackBreadthIsMaxContent : 1;
+    bool m_maxTrackBreadthIsMinContent : 1;
 };
 
 } // namespace blink