Add size check for PaintLayer

third_party/WebKit/Source/core/paint/PaintLayer.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayer.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.cpp b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
index f1f683b47c1d4b69f10391d4f6de1780a9c81348..24891e1a2e7338837dace8734db5a050c70f9f65 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.cpp
@@ -94,6 +94,38 @@ namespace blink {
 
 namespace {
 
+#if !OS(WIN) // Compiler on windows seems to combine bit fields of inner structs.
+
+struct SameSizeAsPaintLayer {
+    virtual ~SameSizeAsPaintLayer() { } // Allocate vtable pointer.
+    int type;
+    int bitFields;
+    void* pointers[13];
+    LayoutUnit layoutUnits[8];
+    int intFields[6];
+    uint64_t compositingReasons[2];
+    struct {
+        IntRect rect;
+        void* pointers[8];
+        int bitFields;
+    } ancestorCompositingInputs;
+    struct {
+        int bitFields;
+    } descendantCompositingInputs;
+    struct {
+        void* pointers[2];
+    } clipper;
+    struct {
+        IntSize size;
+        void* pointer;
+        LayoutRect rect;
+    } previousPaintStatus;
+};
+
+static_assert(sizeof(PaintLayer) == sizeof(SameSizeAsPaintLayer), "PaintLayer should stay small");
+
+#endif // !OS(WIN)
+
 static CompositingQueryMode gCompositingQueryMode =
     CompositingQueriesAreOnlyAllowedInCertainDocumentLifecyclePhases;