Fix supercluster logic.

Source/core/rendering/FastTextAutosizer.h

Index: Source/core/rendering/FastTextAutosizer.h
diff --git a/Source/core/rendering/FastTextAutosizer.h b/Source/core/rendering/FastTextAutosizer.h
index b024b760f73f647909fb83e7ecce2d820bb87755..9de5a1f317f1ff232ae9207c5df9986bebb09741 100644
--- a/Source/core/rendering/FastTextAutosizer.h
+++ b/Source/core/rendering/FastTextAutosizer.h
@@ -91,18 +91,38 @@ public:
     };
 
 private:
+    typedef HashSet<const RenderBlock*> BlockSet;
+
+    // A supercluster represents autosizing information about a set of two or
+    // more blocks that all have the same fingerprint. Clusters whose roots
+    // belong to a supercluster will share a common multiplier and
+    // text-length-based autosizing status.
+    struct Supercluster {
+        explicit Supercluster(const BlockSet* roots)
+            : m_roots(roots)
+            , m_multiplier(0)
+            , m_anyClusterHasEnoughText(false)
+        {
+        }
+
+        const BlockSet* const m_roots;
+        float m_multiplier;
+        bool m_anyClusterHasEnoughText;
+    };
+
     struct Cluster {
-        explicit Cluster(const RenderBlock* root, bool autosize, Cluster* parent)
+        explicit Cluster(const RenderBlock* root, bool autosize, Cluster* parent, Supercluster* supercluster = 0)
             : m_root(root)
             , m_deepestBlockContainingAllText(0)
             , m_parent(parent)
             , m_autosize(autosize)
             , m_multiplier(0)
             , m_textLength(-1)
+            , m_supercluster(supercluster)
         {
         }
 
-        const RenderBlock* m_root;
+        const RenderBlock* const m_root;
         // The deepest block containing all text is computed lazily (see:
         // deepestBlockContainingAllText). A value of 0 indicates the value has not been computed yet.
         const RenderBlock* m_deepestBlockContainingAllText;
@@ -116,6 +136,8 @@ private:
         // Text length is computed lazily (see: textLength). This is an approximation and characters
         // are assumed to be 1em wide. Negative values indicate the length has not been computed.
         int m_textLength;
+        // A set of blocks that are similar to this block.
+        Supercluster* m_supercluster;
     };
 
     enum TextLeafSearch {
@@ -123,9 +145,8 @@ private:
         Last
     };
 
-    typedef HashSet<const RenderBlock*> BlockSet;
-    typedef HashMap<const RenderBlock*, OwnPtr<Cluster> > ClusterMap;
-    typedef Vector<Cluster*> ClusterStack;
+    typedef HashMap<AtomicString, OwnPtr<Supercluster> > SuperclusterMap;
+    typedef Vector<OwnPtr<Cluster> > ClusterStack;
 
     // Fingerprints are computed during style recalc, for (some subset of)
     // blocks that will become cluster roots.
@@ -152,12 +173,15 @@ private:
     void prepareRenderViewInfo(RenderView*);
     bool isFingerprintingCandidate(const RenderBlock*);
     bool clusterHasEnoughTextToAutosize(Cluster*);
+    bool clusterWouldHaveEnoughTextToAutosize(const RenderBlock*);
     float textLength(Cluster*);
     AtomicString computeFingerprint(const RenderBlock*);
-    Cluster* maybeGetOrCreateCluster(const RenderBlock*);
-    Cluster* addSupercluster(AtomicString, const RenderBlock*);
+    Cluster* maybeCreateCluster(const RenderBlock*);
+    Supercluster* getSupercluster(const RenderBlock*);
     const RenderBlock* deepestCommonAncestor(BlockSet&);
     float clusterMultiplier(Cluster*);
+    float superclusterMultiplier(Supercluster*);
+    float multiplierFromBlock(const RenderBlock*);
     void applyMultiplier(RenderObject*, float);
     bool mightBeWiderOrNarrowerDescendant(const RenderBlock*);
     bool isWiderDescendant(Cluster*);
@@ -168,6 +192,7 @@ private:
     RenderObject* nextChildSkippingChildrenOfBlocks(const RenderObject*, const RenderObject*);
 
     const RenderBlock* deepestBlockContainingAllText(Cluster*);
+    const RenderBlock* deepestBlockContainingAllText(const RenderBlock*);
     // Returns the first text leaf that is in the current cluster. We attempt to not include text
     // from descendant clusters but because descendant clusters may not exist, this is only an approximation.
     // The TraversalDirection controls whether we return the first or the last text leaf.
@@ -185,7 +210,7 @@ private:
     // Clusters are created and destroyed during layout. The map key is the
     // cluster root. Clusters whose roots share the same fingerprint use the
     // same multiplier.
-    ClusterMap m_clusters;
+    SuperclusterMap m_superclusters;
     ClusterStack m_clusterStack;
     FingerprintMapper m_fingerprintMapper;
 };