Don't cache subsequence whose layer is not fully contained by repaint rect

Source/platform/graphics/paint/DisplayItem.h

Index: Source/platform/graphics/paint/DisplayItem.h
diff --git a/Source/platform/graphics/paint/DisplayItem.h b/Source/platform/graphics/paint/DisplayItem.h
index 5587149c76a15c6686fa2e0c6b98d6ac4b81039b..2b6c0f22c06abc6053bbf5e04e5412d2258b0b94 100644
--- a/Source/platform/graphics/paint/DisplayItem.h
+++ b/Source/platform/graphics/paint/DisplayItem.h
@@ -189,6 +189,7 @@ public:
         , m_type(type)
         , m_derivedSize(derivedSize)
         , m_skippedCache(false)
+        , m_isUncacheable(false)
 #ifndef NDEBUG
         , m_clientDebugString(client.debugName())
 #endif
@@ -257,6 +258,9 @@ public:
     void setSkippedCache() { m_skippedCache = true; }
     bool skippedCache() const { return m_skippedCache; }
 
+    void setUncacheable() { m_isUncacheable = true; }
+    bool isUncacheable() const { return m_isUncacheable; }

[chrishtr, 2015/09/08 22:48:00]

This can be private.

+
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const { }
 
     // See comments of enum Type for usage of the following macros.
@@ -312,7 +316,7 @@ public:
     static bool isCachedType(Type type) { return isCachedDrawingType(type) || type == CachedSubsequence; }
     bool isCached() const { return isCachedType(m_type); }
     static bool isCacheableType(Type type) { return isDrawingType(type) || type == BeginSubsequence; }
-    bool isCacheable() const { return !skippedCache() && isCacheableType(m_type); }
+    bool isCacheable() const { return !isUncacheable() && isCacheableType(m_type); }
 
     virtual bool isBegin() const { return false; }
     virtual bool isEnd() const { return false; }
@@ -346,6 +350,7 @@ private:
         , m_type(UninitializedType)
         , m_derivedSize(sizeof(*this))
         , m_skippedCache(false)
+        , m_isUncacheable(false)
     { }
 
     DisplayItemClient m_client;
@@ -354,6 +359,7 @@ private:
     const Type m_type : 16;
     unsigned m_derivedSize : 8; // size of the actual derived class
     unsigned m_skippedCache : 1;
+    unsigned m_isUncacheable : 1;
 
 #ifndef NDEBUG
     WTF::String m_clientDebugString;