Don't cache reflection drawings

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 f3acfd4705321f3281d57944172c12f0ac1d87af..523d53b452298b4cbef34fdf5a097f3b4ea21de4 100644
--- a/Source/platform/graphics/paint/DisplayItem.h
+++ b/Source/platform/graphics/paint/DisplayItem.h
@@ -180,22 +180,25 @@ public:
 
     virtual void replay(GraphicsContext&) { }
 
-    DisplayItemClient client() const { return m_id.client; }
-    Type type() const { return m_id.type; }
+    DisplayItemClient client() const { return m_client; }
+    Type type() const { return m_type; }
     bool idsEqual(const DisplayItem& other, Type overrideType) const
     {
-        return m_id.client == other.m_id.client
-            && m_id.type == overrideType
-            && m_id.scopeId == other.m_id.scopeId
-            && m_id.scopeContainer == other.m_id.scopeContainer;
+        return m_client == other.m_client
+            && m_type == overrideType
+            && m_scopeId == other.m_scopeId
+            && m_scopeContainer == other.m_scopeContainer;
     }
 
     void setScope(int scopeId, DisplayItemClient scopeContainer)
     {
-        m_id.scopeId = scopeId;
-        m_id.scopeContainer = scopeContainer;
+        m_scopeId = scopeId;
+        m_scopeContainer = scopeContainer;
     }
 
+    void setSkippedCache() { m_skippedCache = true; }
+    bool skippedCache() const { return m_skippedCache; }
+
     virtual void appendToWebDisplayItemList(WebDisplayItemList*) const { }
 
     // See comments of enum Type for usage of the following macros.
@@ -276,24 +279,22 @@ public:
 
 protected:
     DisplayItem(const DisplayItemClientWrapper& client, Type type)
-        : m_id(client.displayItemClient(), type)
+        : m_client(client.displayItemClient())
+        , m_scopeContainer(nullptr)
+        , m_scopeId(0)
+        , m_type(type)
+        , m_skippedCache(false)
 #ifndef NDEBUG
         , m_clientDebugString(client.debugName())
 #endif
     { }
 
 private:
-    struct Id {

[chrishtr, 2015/06/02 17:06:56]

What's the point of flattening the struct? Is it not possible to pack the memory
otherwise?

[Xianzhu, 2015/06/02 17:36:34]

Otherwise it would be:
  struct Id {
     ...
  };
  bool m_skippedCache; // not part of Id

Flattening the struct also makes it possible to borrow more bits from m_type
(e.g. we can add bits to avoid the virtual isXXX functions).

-        Id(DisplayItemClient c, Type t) : client(c), type(t), scopeId(0), scopeContainer(nullptr)
-        {
-            ASSERT(c);
-        }
-
-        const DisplayItemClient client;
-        const Type type;
-        int scopeId;
-        DisplayItemClient scopeContainer;
-    } m_id;
+    const DisplayItemClient m_client;
+    DisplayItemClient m_scopeContainer;
+    unsigned m_scopeId : 16;

[pdr., 2015/06/02 17:16:08]

This seems dangerous in the future and doesn't do anything today.

[Xianzhu, 2015/06/02 17:36:35]

Restored back to 'int'.

+    const Type m_type : 15;
+    bool m_skippedCache : 1;
 
 #ifndef NDEBUG
     WTF::String m_clientDebugString;